From The DOE’s Brookhaven National Laboratory Via “phys.org” : “Physicists track sequential ‘melting’ of upsilons”

From The DOE’s Brookhaven National Laboratory

Via

“phys.org”

Scientists used the STAR detector at the Relativistic Heavy Ion Collider (RHIC) to track how upsilon particles dissociate in quark-gluon plasma. These upsilons are made of a bottom quark and antibottom quark held together by gluons with different binding energies: a tightly bound ground state (left), an intermediate variety (right), and the largest, most loosely bound state (center). Credit: Brookhaven National Laboratory.

Scientists using the Relativistic Heavy Ion Collider (RHIC)[below] to study some of the hottest matter ever created in a laboratory have published their first data showing how three distinct variations of particles called upsilons sequentially “melt,” or dissociate, in the hot goo. The results, just published in Physical Review Letters [below], come from RHIC’s STAR detector [below], one of two large particle tracking experiments at this U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research.

The data on upsilons add further evidence that the quarks and gluons that make up the hot matter—which is known as a quark-gluon plasma (QGP)—are “deconfined,” or free from their ordinary existence locked inside other particles such as protons and neutrons. The findings will help scientists learn about the properties of the QGP, including its temperature.

“By measuring the level of upsilon suppression or dissociation we can infer the properties of the QGP,” said Rongrong Ma, a physicist at DOE’s Brookhaven National Laboratory, where RHIC is located, and Physics Analysis Coordinator for the STAR collaboration. “We can’t tell exactly what the average temperature of the QGP is based solely on this measurement, but this measurement is an important piece of a bigger picture. We will put this and other measurements together to get a clearer understanding of this unique form of matter.”

Setting quarks and gluons free

Scientists use RHIC, a 2.4-mile-circumference “atom smasher,” to create and study QGP by accelerating and colliding two beams of gold ions—atomic nuclei stripped of their electrons—at very high energies. These energetic smashups can melt the boundaries of the atoms’ protons and neutrons liberating the quarks and gluons inside.

One way to confirm that collisions have created QGP is to look for evidence that the free quarks and gluons are interacting with other particles. Upsilons, short-lived particles made of a heavy quark-antiquark pair (bottom-antibottom) bound together, turn out to be ideal particles for this task.

“The upsilon is a very strongly bounded state; it’s hard to dissociate,” said Zebo Tang, a STAR collaborator from the University of Science and Technology of China. “But when you put it in a QGP, you have so many quarks and gluons surrounding both the quark and antiquark, that all those surrounding interactions compete with the upsilon’s own quark-antiquark interaction.”

These “screening” interactions can break the upsilon apart—effectively melting it and suppressing the number of upsilons the scientists count.

“If the quarks and gluons were still confined within individual protons and neutrons, they wouldn’t be able to participate in the competing interactions that break up the quark-antiquark pairs,” Tang said.

Upsilon advantages

Scientists have observed such suppression of other quark-antiquark particles in QGP—namely J/psi particles (made of a charm-anticharm pair). But upsilons stand apart from J/psi particles, the STAR scientists say, for two main reasons: their inability to reform in the QGP and the fact that they come in three types.

Before we get to reforming, let’s talk about how these particles form. Charm and bottom quarks and antiquarks are created very early in the collisions—even before the QGP. At the instant of impact, when the kinetic energy of the colliding gold ions is deposited in a tiny space, it triggers the creation of many particles of matter and antimatter as energy transforms into mass through Albert Einstein’s famous equation, E=mc2. The quarks and antiquarks partner up to form upsilons and J/psi particles, which can then interact with the newly formed QGP.

But because it takes more energy to make heavier particles, there are many more lighter charm and anticharm quarks than heavier bottom and antibottom quarks in the particle soup. That means that even after some J/psi particles dissociate, or “melt,” in the QGP, others can continue to form as charm and anticharm quarks find one another in the plasma. This reformation happens only very rarely with upsilons because of the relative scarcity of heavy bottom and antibottom quarks. So, once an upsilon dissociates, it’s gone.

“There just aren’t enough bottom-antibottom quarks in the QGP to partner up,” said Shuai Yang, a STAR collaborator from South China Normal University. “This makes upsilon counts very clean because their suppression isn’t muddied by reformation the way J/psi counts can be.”

The other advantage of upsilons is that, unlike J/psi particles, they come in three varieties: a tightly bound ground state and two different excited states where the quark-antiquark pairs are more loosely bound. The most tightly bound version should be hardest to pull apart and melt at a higher temperature.

“If we observe the suppression levels for the three varieties are different, maybe we can establish a range for the QGP temperature,” Yang said.

First time measurement

These results mark the first time RHIC scientists have been able to measure the suppression for each of the three upsilon varieties.

They found the expected pattern: The least suppression/melting for the most tightly bound ground state; higher suppression for the intermediately bound state; and essentially no upsilons of the most loosely bound state—meaning all the upsilons in this last group may have been melted. (The scientists note that the level of uncertainty in the measurement of that most excited, loosely bound state was large.)

“We don’t measure the upsilon directly; it decays almost instantly,” Yang explained. “Instead, we measure the decay ‘daughters.’”

The team looked at two decay “channels.” One decay path leads to electron-positron pairs, picked up by STAR’s electromagnetic calorimeter. The other decay path, to positive and negative muons, was tracked by STAR’s muon telescope detector.

In both cases, reconstructing the momentum and mass of the decay daughters establishes if the pair came from an upsilon.

And since the different types of upsilons have different masses, the scientists could tell the three types apart.
“This is the most anticipated result coming out of the muon telescope detector,” said Brookhaven Lab physicist Lijuan Ruan, a STAR co-spokesperson and manager of the muon telescope detector project. That component was specifically proposed and built for the purpose of tracking upsilons, with planning back as far as 2005, construction beginning in 2010, and full installation in time for the RHIC run of 2014—the source of data, along with 2016, for this analysis.

“It was a very challenging measurement,” Ma said. “This paper is essentially declaring the success of the STAR muon telescope detector program. We will continue to use this detector component for the next few years to collect more data to reduce our uncertainties about these results.”

Collecting more data over the next few years of running STAR, along with RHIC’s brand new detector, sPHENIX [below], should provide a clearer picture of the QGP. sPHENIX was built to track upsilons and other particles made of heavy quarks as one of its major goals.

“We’re looking forward to how new data to be collected in the next few years will fill out our picture of the QGP,” said Ma.

Additional scientists from the following institutions made significant contributions to this paper: National Cheng Kung University, Rice University, Shandong University, Tsinghua University, University of Illinois at Chicago.

The research was funded by the DOE Office of Science (NP), the U.S. National Science Foundation, and a range of international organizations and agencies listed in the scientific paper. The STAR team used computing resources at the Scientific Data and Computing Center at Brookhaven Lab, the National Energy Research Scientific Computing Center (NERSC) at DOE’s Lawrence Berkeley National Laboratory, and the Open Science Grid consortium.

Physical Review Letters

See the full article here .

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Brookhaven Campus. Credit: BNL.

One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc. (AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966.

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS).

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

BNL National Synchrotron Light Source.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider (CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, it was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] as the future Electron–ion collider (EIC) in the United States.

Electron-Ion Collider (EIC) at DOE’s Brookhaven National Laboratory to be built inside the tunnel that currently houses the Relativistic Heavy Ion Collider [RHIC]. Credit: BNL.

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Large Hadron Collider(LHC). Credit: CERN.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map. Credit: CERN.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung] By now iconic image of (CH)[CERN] ATLAS. Credit: CERN.

It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] near Geneva, Switzerland.

Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .

DOE’s Fermi National Accelerator Laboratory DUNE LBNF from FNAL to Sanford Underground Research Facility, Lead, South Dakota.

BNL Center for Functional Nanomaterials. Credit: BNL.

DOE’s Brookhaven National Laboratory NSLS II. Interior. Credit: BNL.

DOE’s Brookhaven National Laboratory NSLS II. Credit: BNL.

DOE’s Brookhaven National Laboratory(US) RHIC Campus. Credit: BNL.

BNL RHIC’s newly enhanced STAR detector. The house-size STAR detector at the Relativistic Heavy Ion Collider (RHIC) acts like a giant 3D digital camera to track particles emerging from particle collisions at the center of the detector.

DOE’s Brookhaven National Laboratory(US)/RHIC Phenix detector. Credit: BNL..

Brookhaven sPhenix Assembly. Credit: BNL.

BNL RHIC Schematic view of the proposed sPHENIX detector. Credit: BNL.

BNL RHIC inner hadronic calorimeter being installed in the sPHENIX Detector. Credit: BNL.

From The Relative Heavy Ion Collider (RHIC) At The DOE’s Brookhaven National Laboratory Via “Scientific American” : “Tiny Bubbles of Primordial Soup Re-create Early Universe”

From The Relative Heavy Ion Collider (RHIC)

At

The DOE’s Brookhaven National Laboratory

Via

“Scientific American”

3.1.23
Clara Moskowitz

A technician installs cables on the new sPHENIX detector [below] at the Relativistic Heavy Ion Collider (RHIC) [below] at The DOE’s Brookhaven National Laboratory on Long Island, NY. Inside sPHENIX’s cylindrical interior, atomic nuclei will collide to make droplets of a plasma that existed at the beginning of the cosmos. Credit: Christopher Payne.

“Imagine you have a microscope that would let you see a single atom up close. Let’s say it’s a hydrogen atom, the smallest kind. Zoom in past the single electron orbiting at the outskirts, and you’ll find the nucleus—in this case a lone proton. High school physics would have you believe that inside this proton you’ll find a simple triad of three fundamental particles called quarks—two up quarks and one down quark. But the reality inside a proton is so much more complex that physicists are still trying to figure out its inner structure and how its constituents combine to produce its mass, spin and other properties.

The quark structure of the proton. 16 March 2006 Arpad Horvath.

The three quarks in the basic picture of the interior of a proton are merely the “valence quarks”—buoys bobbing on top of a roiling sea of quarks and antiquarks (their antimatter counterparts), as well as the sticky “gluon” particles that hold them together. The total number of quarks and gluons inside a proton is always changing. Quark-antiquark pairs are constantly popping in and out of existence, and gluons tend to split and multiply, especially when a proton gains speed. It’s basically pure chaos. The strong force—the most powerful of the four fundamental forces of nature—keeps this mess confined to the insides of protons and neutrons. Except when it doesn’t.

In the first tiny fractions of a second after the big bang, the universe was too hot and dense for the strong force to bind quarks and gluons together. Instead they became an ocean—a perfect liquid of particles flowing with almost no resistance, called a quark-gluon plasma. This stage of the universe’s history ended quickly. Within 10^-6 second, quarks and gluons were caged inside protons and neutrons. But then, 13.7 billion years later, physicists learned how to re-create the quark-gluon plasma inside particle accelerators. When two large atomic nuclei (such as gold) smash together at nearly the speed of light, the collision produces the temperatures and pressures needed for droplets of quark-gluon plasma to form, briefly, before disintegrating.

The machines that capture these collisions are towering constructions, stacks of detectors and instruments arranged in concentric rings, all of it connected with thousands of wires. When I visited two of them last year at the DOE’s Brookhaven National Laboratory’s Long Island campus, I marveled at the painstaking work of large teams of technicians climbing multiple levels of scaffolding to access the devices. Standing underneath such a colossus feels like witnessing the pinnacle of what humans can achieve—these are some of the largest and most intricate machines ever built, all to study a drop of primordial ooze even smaller than an atom. Investigating droplets of quark-gluon plasma gives scientists a chance to learn how matter got its start. ‘This is what filled the entire universe about 10 microseconds after the big bang,’ says Bjoern Schenke, a Brookhaven theoretical physicist. ‘Studying it allows us to go back in time as much as we possibly can.’

The research is also a window into the strong force, the least understood of all nature’s forces. This force is described by a theory called quantum chromodynamics (QCD), which is so complicated that scientists can almost never use it to calculate anything directly. The best they can do is to use supercomputers running simulations to get approximate answers. “As human beings, we want to understand nature, and part of understanding nature is to understand quantum chromodynamics and the strong force,” says physicist Haiyan Gao, associate laboratory director for nuclear and particle physics at Brookhaven. “We need to do experiments on quark-gluon plasma to understand how this theory works.”

In April 2023 Brookhaven scientists will turn on the latest experiment designed to study quark-gluon plasma. The device, called sPHENIX [below], is one of two detectors at the lab’s Relativistic Heavy Ion Collider (RHIC)[below], one of the largest particle accelerators in the world. The other detector there, the Solenoidal Tracker at RHIC (STAR)[below], is also reopening after major upgrades. Across the Atlantic at the European CERN physics lab near Geneva, the globe’s biggest accelerator, the Large Hadron Collider (LHC) [below], recently began a new run with upgraded detectors and an ability to smash many more atoms at once.

Together these tools should reveal the most detailed picture yet of this primordial fluid, bringing us closer to unraveling the secrets of the tiniest constituents of matter.

A Surprising Discovery

Scientists predicted quark-gluon plasma long before they discovered it—although they expected it to take a very different form. The predictions came about in the 1970s and 1980s, following the discovery of quarks in the late 1960s and of gluons in 1979. Physicists expected that quarks and gluons, when freed from nuclei, would take the form of a uniformly expanding gaseous substance. ‘Usually fluids turn to gas as they get hotter,’ says Berndt Mueller, a physicist at Duke University, who started working on theoretical models for quark-gluon plasma in the 1980s. It was a reasonable assumption: quarks and gluons aren’t released from nuclei until they reach temperatures of trillions of degrees.

Mueller was attracted to the field because the theoretical possibilities were wide open, and experimental data were set to start arriving soon. “At that time I was about 30 years old, and you look around for new things you could work on where you have lots of interesting stuff to discover.” During this era physicists were developing technologies to smash together heavy ions—nuclei with dozens of protons and neutrons inside them—and they expected these collisions to generate temperatures and densities that would break subatomic particles apart. The earliest heavy ion collisions, which took place in the 1970s at The DOE’s Lawrence Berkeley National Laboratory, weren’t powerful enough to create quark-gluon plasma, but in 1986 the Super Proton Synchrotron (SPS) accelerator at CERN began its own heavy ion collisions, and those produced the first evidence for the new state of matter.

The Super Proton Synchrotron (SPS), CERN’s second-largest accelerator. (Image: Julien Ordan/CERN).

It took a while. The CERN team eventually announced their findings in 2000, but even then researchers were divided over whether the data were strong enough to claim a discovery. That same year Brookhaven’s RHIC opened and started crashing heavy ions at higher energies than at the SPS. Within five years this accelerator had amassed enough data that physicists declared quark-gluon plasma officially found.

It wasn’t what they had imagined. Instead of an expanding gas, the quark-gluon plasma looked like a liquid—a nearly perfect one, with almost no viscosity. In a gas, particles act individually; in a liquid, particles move cohesively. The stronger the interactions among particles—the more they can pull one another along—the “better” the liquid is at being a liquid. The RHIC observations showed that quark-gluon plasma exhibited less resistance to flow than any substance ever known. This, Mueller says, ‘was very much unexpected.’

Credit: Jason Drakeford.

In 2010 RHIC researchers announced the first measurement of the quark-gluon plasma’s temperature. It was a scorching four trillion degrees Celsius, far hotter than any other matter ever created by humans, and about 250,000 times hotter than the middle of the sun. ‘Usually the hotter something becomes, the less of a perfect fluid it becomes,’ Mueller says. ‘But in this case, it’s the opposite—when you reach the critical temperature, it turns into a liquid.’ Scientists suspect the strong force is behind this odd behavior. When the particles become hot enough to escape from protons and neutrons, the strong force acts over the entire plasma, causing the collective mass of particles to interact strongly with one another.

The Mystery of the Strong Force

One of the biggest open questions about quark-gluon plasma is when, exactly, the quarks and gluons break out of their confinement. ‘Where is the boundary between usual matter and quark-gluon plasma?’ Gao asks. ‘Where is the so-called critical point where the nuclear matter and the quark-gluon plasma coexist?’ Understanding where that transition happens, and how many particles it takes to initiate the collective behavior, will be among the main goals of the new and upgraded experiments.

Another question is whether quark-gluon plasma is a fractal—that is, whether its structure has a complex, repeating pattern that appears the same at every scale, whether you zoom out or in. Some researchers have been arguing that quark-gluon plasma has these two properties and that fractal theory could offer insights into how the plasma behaves. ‘There is evidence that we have fractal structure in quark-gluon plasma,’ says Airton Deppman, a physicist at the University of São Paulo’s Institute of Physics. ‘We are also investigating if the fractal structure survives the phase transition’ from plasma to proton.

Answering these questions could help with a larger goal: understanding the strong force, the most confusing of nature’s fundamental forces. Quantum chromodynamics describes the interactions between quarks and gluons by ascribing them a property called color charge. This color charge is akin to electrical charge in the theory of electromagnetism, and it also explains why quantum chromodynamics so quickly gets out of hand. Whereas electromagnetism has only two charges—positive or negative—QCD has three—red, green or blue. And antimatter particles can carry antired, antigreen or antiblue charge.

In electromagnetism, the particle that carries the electromagnetic force, the photon, is itself electrically neutral, which keeps things somewhat simple. In QCD, though, the force carrier, the gluon, also carries a color charge and can interact through the strong force with itself and with quarks. These self-interactions and extra charges have made QCD prohibitively complicated. ‘You can write down the theory essentially in two lines, but actually solving it has not been really achieved,’ Schenke says. ‘The process of confinement—how gluons and quarks are being trapped in the proton, for example—has not been solved.’

RHIC’s tunnels “stochastic cooling kickers” push the particles within the rings closer together to correct for their tendency to spread out as they travel. Credit: Christopher Payne.

Scientists hope that studying quark-gluon plasma—the only situation in which scientists have ever been able to probe unbound quarks—could reveal more about how confinement works. ‘One way to get at that is to free them and see how they then recombine again to protons, neutrons and other particles that we can observe from the detector,’ Schenke adds. Thus, experimental data from heavy-ion collisions can be used to better understand the mechanisms within QCD that lead to confinement.

New and Improved

With the RHIC’s new experiment, sPHENIX [below], and the upgraded STAR detector [below], scientists should be able to take the most precise measurements of the plasma yet. For instance, sPHENIX has a superconducting magnet that is roughly three times stronger than STAR’s. ‘That’s important for many of the things we want to measure,’ says David Morrison, a Brookhaven physicist working on the new machine. ‘If you have a collision, particles come out every which way, and then the magnetic fields bend their paths. We can look at that to start unraveling what kind of particle was it and how much energy and momentum did it have?’ The team is hoping to spot composite particles called upsilons, for example. Upsilons, which contain a bottom quark and an anti-bottom quark, can form in collisions and then fly through the quark-gluon plasma, acting as test probes to reveal how the plasma changes them. ‘We can really unravel the physics that underlies a lot of the weird properties of the quark-gluon plasma,’ he adds.

The experiment will also benefit from being able to record much more data—meaning many more collisions and the particles they result in—than was possible before. STAR captures around 10 petabytes of data a year; sPHENIX will take around 150 petabytes annually. That increase will bring previously unanswerable questions within reach.

STAR also has novel capabilities, such as new calorimeters for measuring the energies of particles and tracking detectors for identifying particles with different electrical charges. Among the most significant additions, says Brookhaven’s Lijuan Ruan, one of STAR’s spokespeople, are ‘forward’ detectors that can record particles flying out of collisions at wider angles than before, including particles moving in the same direction as the beams that fed into the crash. ‘Now that’s basically it—we’re not going to upgrade anymore,’ says Ruan, who has been working on STAR for many years and helped to build some of its early components around 20 years ago as a graduate student. ‘It’s a different feeling when you just use a detector, compared to when you actually build it and the entire collaboration can use it,’ she says. ‘I feel proud.’ STAR, which was among the original RHIC experiments that helped to discover quark-gluon plasma, will operate for another three years before shutting down.

This Particle Accelerator Makes A Substance That Hasn’t Existed in 13 Billion Years: ‘Quark Soup’.

In Europe, the LHC recently began its third run, which started in July 2022 and will continue until 2025. After the latest upgrades, LHC scientists can analyze about 100 times more lead-lead collisions than they could during the first two runs. The extra collisions will also increase the precision of measurements. ‘One of the important goals for run three is to precisely quantify the properties of the quark-gluon plasma and connect them to the dynamics of its constituents,’ says Luciano Musa, a member of the ALICE experiment at the LHC.

Compared with the RHIC experiments, the LHC collisions occur at higher energies and produce a hotter, denser and longer-lived quark-gluon plasma. These energetic smashups also create a larger variety of particles that scientists can use to probe the plasma’s properties. ‘The studies at RHIC and LHC really go hand in hand,’ Musa says. ‘Studying the properties of relativistic nuclear collisions at different energy scales and with different collision systems at CERN and RHIC allows us to gain a more profound and comprehensive understanding of nuclear matter.’

The different energy ranges reveal different aspects of the plasma. Raghav Kunnawalkam Elayavalli, a physicist at Vanderbilt University, did their Ph.D. work at the LHC, but recently became a member of the STAR and sPHENIX collaborations to focus on the particles coming out of lower-energy collisions. ‘They are closer to the scale of the plasma; they talk to it a lot more,’ Kunnawalkam Elayavalli says. ‘Think of it like a party: there’s a lot of people, and you’re making a beeline to the exit. But if you’re kind of slow and you don’t want to leave that fast, you get a chance to talk to people on your way out.’ Because particles flying through the quark-gluon plasma at RHIC take longer to move through it, they can extract more information from it. ‘The things we’re trying to measure are the transport properties—the average distance you can go without interacting with another particle,’ they add. ‘It tells us about the fundamental scale of the plasma.’

Back to the Beginning

The new era of quark-gluon plasma experiments should move the field beyond the basics and toward concrete answers to long-standing questions. ‘There was a period of physics at RHIC that was basically, ‘Wow, this happening—this is new physics,’ Kunnawalkam Elayavalli says. ‘And now we are in the precision era. We can ask, ‘Why is this happening?’

RHIC and the LHC are leading the effort to understand this special state of matter, but upcoming experiments elsewhere will also add insights. At CERN, alongside the LHC, the SPS accelerator is still running. A planned experiment there called NA61/SHINE will collide moving ions into a stationary target to measure the critical point when protons and neutrons turn into quark-gluon plasma.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] NA61.

A second fixed-target experiment, the Facility for Antiproton and Ion Research (FAIR) at GSI Darmstadt in Germany, is due to open in 2028.

FAIR Facility for Antiproton and Ion Research, Germany

And at the Joint Institute for Nuclear Research in Dubna near Moscow, a collider called the Nuclotron-based Ion Collider fAcility (NICA) will also probe the critical point.

Nuclotron-based Ion Collider fAcility (NICA)

‘It’s an exciting time,’ Mueller says. ‘We know the quark-gluon plasma existed in the early universe, but we have no way of probing that. This is our way of probing a physics situation that otherwise we don’t have any hope to reach.’”

See the full article here .

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DOE’s Brookhaven National Laboratory Relative Heavy Ion Collider.

The Physics of RHIC
Physicists from around the world are using the Relativistic Heavy Ion Collider to explore some of Nature’s most basic — and intriguing — ingredients and phenomena. Here’s a look at the physics of RHIC in plain English.

Heavy Ion Collisions

RHIC is the first machine in the world capable of colliding heavy ions, which are atoms which have had their outer cloud of electrons removed. RHIC primarily uses ions of gold, one of the heaviest common elements, because its nucleus is densely packed with particles.

RHIC collides two beams of gold ions head-on when they’re traveling at nearly the speed of light (what physicists call relativistic speeds). The beams travel in opposite directions around RHIC’s 2.4-mile, two-lane “racetrack.” At six intersections, the lanes cross, leading to an intersection. When ions collide at such high speeds fascinating things happen.

If conditions are right, the collision “melts” the protons and neutrons and, for a brief instant, liberates their constituent quarks and gluons. Just after the collision, thousands more particles form as the area cools off. Each of these particles provides a clue as to what occurred inside the collision zone. Physicists sift through those clues for interesting information.

Brookhaven Campus

One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University-SUNY the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5,300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc., but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966.

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS).

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

BNL National Synchrotron Light Source.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider(CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, It was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility) as the future Electron–ion collider (EIC)

Brookhaven Lab Electron-Ion Collider (EIC) to be built inside the tunnel that currently houses the RHIC.

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] Large Hadron Collider(LHC).

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] map.

Iconic view of the European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN] ATLAS detector.

It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN] near Geneva, Switzerland.

Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .

DOE’s Fermi National Accelerator Laboratory DUNE LBNF from FNAL to Sanford Underground Research Facility, Lead, South Dakota, USA.

BNL Center for Functional Nanomaterials.

BNL National Synchrotron Light Source II.

BNL NSLS II.

BNL Relative Heavy Ion Collider Campus.

BNL/RHIC Star Detector.

BNL RHIC’s newly enhanced STAR detector. The house-size STAR detector at the Relativistic Heavy Ion Collider (RHIC) acts like a giant 3D digital camera to track particles emerging from particle collisions at the center of the detector.

BNL/RHIC Phenix detector.

Brookhaven sPhenix Assembly

BNL RHIC Schematic view of the proposed sPHENIX detector.

BNL RHIC inner hadronic calorimeter being installed in the sPHENIX Detector.

Quark-Gluon Plasma from BNL Relative Heavy Ion Collider.

Particles circulate along RHIC’s 2.4-mile ring at close to the speed of light before colliding inside detectors sPHENIX and STAR. Credit: Christopher Payne.

RHIC’s tunnels “stochastic cooling kickers” push the particles within the rings closer together to correct for their tendency to spread out as they travel. Credit: Christopher Payne.

From The DOE’s Brookhaven National Laboratory: “sPHENIX Assembly Update – Magnet Mapped and Detectors Prepared”

From The DOE’s Brookhaven National Laboratory

12.23.22
Kelly Zegers
kzegers@bnl.gov

Collaborators’ sights are set on a spring 2023 start-up for advanced particle detector.

From left: The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] magnet mapping experts Nicola Pacifico, Francois Garnier, Raphael Dumps, Pritindra Bhowmick visited sPHENIX in November to map the field generated by the superconducting magnet at the heart of the sPHENIX detector. Credit: BNL.

BNL Superconducting magnet. Credit: BNL.

Physicists, engineers, and technicians at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory are rounding out the year with key developments to a house-sized particle detector that will begin capturing collision snapshots for the first time next spring.

The state-of-the-art, three-story, 1,000-ton detector—known as sPHENIX [below]—will precisely track particles streaming from collisions at the Relativistic Heavy Ion Collider (RHIC) [below], a DOE Office of Science user facility for nuclear physics research. It’s an ongoing makeover of the PHENIX experiment [below], which took data at RHIC from 2000 until 2016. The upgraded, state-of-the-art sPHENIX will enable scientists to better understand the properties of quark-gluon plasma (QGP) —a soup of subatomic particles that are the inner building blocks of protons and neutrons. Scientists want to measure those particles to learn more about how those building blocks interact to form the visible matter that makes up our world.

With the recent completion of essential particle-tracking components and a project to map the magnetic field of a superconducting electromagnet at the detector’s core, sPHENIX crews are gearing up for final installations.

“There’s this whole choreography of a very intricate process of how these remaining pieces go together that’s going to play out in the next months and have us in shape to take data in the spring,” said Brookhaven Lab nuclear physicist and sPHENIX co-spokesperson David Morrison.

CERN crew maps magnetic field

A central component of sPHENIX is a 20-ton cylindrical superconducting solenoid magnet [below]. It was once the centerpiece of an experiment called BaBar at SLAC National Accelerator Laboratory in California.

SLAC National Accelerator Laboratory BaBar. Credit: SLAC.

SLAC National Accelerator LaboratoryBaBar. Credit: SLAC.

Crews transported it across the country in 2015, tested it at low-field in 2016 and high-field in 2018, and carefully installed it at sPHENIX last year.

The magnet generates a precise and uniform magnetic field—1.4 Tesla, or about as strong as the magnet used for magnetic resonance imaging (MRI) scans. The powerful field will bend the trajectories of charged particles that are among the “debris” produced when nuclei collide at RHIC.

Remaining detectors soon to be layered inside the magnet’s drum will measure very accurately the position of the particles that stream out of these nuclear smashups, from which other properties can be obtained. Scientists seek to “connect the dots” of those measurements to discern very small differences among three kinds of “parent” particles called upsilons. The upsilon data is only one of numerous studies with sPHENIX at RHIC which will reveal clues about how QGP transitions from a hot soup of quarks and gluons to matter as we know it.

But before these final tracking components can be installed, the sPHENIX crew sought to map the solenoid’s magnetic field.

“Once you fill up the middle of the magnet, you can’t place a mapping machine inside,” said Brookhaven physicist Kin Yip.

A team from CERN, Europe’s particle physics laboratory, came to Brookhaven in November to tackle the precision task.

“CERN’s detector technologies group are the world experts in magnet mapping,” Yip said.

The CERN team used the same mapping machine they’d previously used to map the magnet that forms the backbone of the ATLAS experiment at CERN’s Large Hadron Collider.

CERN ATLAS Magnet System. Credit: CERN.

The mapping machine, shipped from Geneva, Switzerland, fit into precision rails inside of the magnet’s drum, where some panels of the sPHENIX electromagnetic calorimeter (EMCal) [below]—which will measure different types of charged and uncharged particles in RHIC collisions—had not yet been installed. The cryogenic group from Brookhaven’s Collider-Accelerator Department used liquid helium to cool the solenoid’s superconducting cables to 4.6 degrees Kelvin (-451.4 degrees Fahrenheit)—the temperature needed to generate the magnetic field. Two arms run by air-powered motors rotated like propellers to measure the magnetic field as crews stepped the machine along points from one end of the cylindrical magnet to the other. (Technicians installed the final EMCal segments soon after the mapping project ended.)

“We thank Brookhaven Lab and in particular the people at sPHENIX for tasking us with the mapping of the sPHENIX solenoid,” said Nicola Pacifico of CERN’s mapping group, which included Francois Garnier, Raphael Dumps, Pritindra Bhowmick. “Every mapping campaign is an R&D exercise on its own, presenting its specific challenges. We enjoyed the support of a very competent team on site, which allowed us to complete the mapping in a timely manner. We wish sPHENIX and its team full success in its physics programme, and au revoir until the next mapping at Brookhaven Lab!”

sPHENIX scientists had been using a calculated map of the solenoid’s magnetic field to run RHIC collision simulations. The new precision measurements will increase the accuracy of deciphering data from the complex experiment once it’s up and running.

“In general, in experimental physics, more information is better than less information,” said John Haggerty, a Brookhaven physicist who led the acquisition of the magnet in the early days of sPHENIX. “We can only calculate what we think we built, not what we may have inadvertently built. Now, we have the best possible map.”

Cameron Dean, a postdoc at the Massachusetts Institute of Technology, with the complex MVTX detector, which experts from The DOE’s Lawrence Berkeley National Laboratory assembled and shipped to Brookhaven Lab. “I’ve worked on the MVTX project for almost 4 years now and it has been amazing to see it progress from individual pixels chips to a fully-fledged detector,” Dean said. “I can’t wait to turn it on inside sPHENIX in a few months to see it record the very first collisions in a brand new experiment.” Credit: BNL.

Key sub-detector arrives at Brookhaven

The massive magnet isn’t the only major detector component that made a cross-country trek to sPHENIX. Pieces of a pixel-based vertex detector known as MVTX, were built at CERN, then shipped to The DOE’s Lawrence Berkeley National Laboratory for expert assembly, before arriving safely at Brookhaven in October. The detector was shipped in two halves for the 3,000-mile cross-country road trip. Crews used a truck with special suspension and took care to consider a safe route and weather conditions.

The MVTX is one of three components that will work together to measure the position to determine the momentum of all charged particles emerging from RHIC’s collisions. (The other two are an Intermediate Silicon Strip Tracker and a Time Projection Chamber (TPC) being built at Stony Brook University.

Technicians, engineers, postdocs, and scientists from Japan, Taiwan, and the U.S. have built the INTT detector, which consists of four barrel layers of silicon strip semiconductor detectors. From left: Maya Shimomura, Robert Pisani, Cheng-Wei Shih, Genki Nukazuka, Seberg Nicholas, Raul Cecato, Ivan Kotov, Salvatore Polizzo, Itaru Nakagawa, and Rachid Nouicer. Credit: BNL.

The MVTX, which will sit within the sPHENIX magnet’s central core, offers a very precise answer to the question: did a particle come exactly from the collision or even a fraction of a hair’s width away? It turns out that differences of such tiny distances can make a big difference.

“Thousands of particles come out of our collisions,” Morrison explained. “Some of those particles decay, turning into other types of particles almost right away—making it maybe 50 microns, about the thickness of a strand of hair. MVTX tells us extremely precisely where particles came from, with a precision of about five microns, so we know if the particle was created in the collision itself or is a product of such as decay.”

The part of MVTX that actually makes measurements is compact—about a foot long, 3.5 inches in diameter, and weighing in at about 3 ounces. All together, MVTX is made up of three overlapping layers of silicon sensors, which line two halves of a carbon fiber tube. At one end, the tube widens like the bell of a trumpet to fit lots of cables and fibers that power and readout the detector.

 “In this compact package there are 300 million channels, elements that can say ‘I saw something,’” said Edward O’Brien, the sPHENIX project director. “If we think of those channels as pixels, MVTX has a factor of 40 more pixels than your high-definition TV crammed into a space that’s over 20 times smaller.”

Before installing the pixel-based detector early next year, sPHENIX engineers and technicians will practice placing a mockup of this delicate component around the experiment’s beam pipe., They’ll have only a tiny amount of clearance—about a millimeter—to slide the device into its final position after the other detector components are installed. “It’s like playing the game ‘Operation’ in reverse,” Morrison said. When it comes time to put that final piece in place, he says, the sPHENIX crew will be ready.

Tracking super-fast, overlapping events

Meanwhile the team is making progress on those other particle-tracking components.

With a response time of 60 nanoseconds—60 billionths of second—the INTT will be key in capturing continuous snapshots of 15,000 particle collisions per second, more than three times faster than the former PHENIX detector.

The INTT takes measurements in the space where MVTX and TPC do not, allowing physicists to reconstruct a complete particle track. It’s super-fast response time enables it to distinguish which tracks come from overlapping events when collisions are piling up.

The sub-detector was completed in mid-September by an international collaboration that included technicians, engineers, postdocs, and scientists from Japan, Taiwan, and the U.S. The project is funded primarily through the RIKEN BNL Research Center (RBRC) with additional U.S and international contributions.

The INTT consists of four layers of overlapping silicon strips that form a semiconductor particle detector based on ionizing radiation detection. The layers sit in two halves of a 10-foot-long cylinder. Bringing the two-halves of the detector together for testing, and soon installation, was a tricky task with many moving parts.

“It’s like flying a 747 airplane,” said Rachid Nouicer, a Brookhaven Lab nuclear physicist, RBRC senior visiting scientist, Stony Brook University adjunct professor, and co-manager of the INTT detector construction.

To ensure a “safe landing” the INTT assembly team used a machine with two “claws” that picked up each half and pressed them together while technicians tightened screws and knobs around the device. They had to be careful to prevent any cracks in the silicon strips. They also needed to ensure there are no gaps between overlapping silicon layers so the detector can receive all particle signals when its operational.

“Physics is always moving towards precision and detector technology has to keep up with it—we want detectors to be faster, more precise,” Nouicer said. “It’s a great accomplishment to see all the INTT detector’s channels working. Now, we want to do physics with it.”

As work progresses on the TPC, a gas tracking detector, at Stony Brook, the time for physics is fast approaching. Stay tuned for another update on that detector component.

“We’re right at the end of detector component construction. O’Brien said. “We’re done within errors. The challenge ahead is completing installation in the next few months”

“As you can see, the construction and assembly of these complex detector components is a major international effort,” said sPHENIX co-spokesperson Gunther Roland, a physicist at the Massachusetts Institute of Technology. “This work brings together so many great physicists from all over the world—80 universities and labs from 14 countries and close to 400 collaborators —to make the vision for this detector and the science it will enable a reality.”

The upgrade and operations at RHIC are funded by the DOE Office of Science (NP).

See the full article here .

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Brookhaven Campus

One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc. (AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966.

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS).

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

BNL National Synchrotron Light Source.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider (CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, it was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] as the future Electron–ion collider (EIC) in the United States.

Electron-Ion Collider (EIC) at DOE’s Brookhaven National Laboratory to be built inside the tunnel that currently houses the Relativistic Heavy Ion Collider [RHIC].

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Large Hadron Collider(LHC).

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

Iconic view of the European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] ATLAS detector.

It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] near Geneva, Switzerland.

Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .

DOE’s Fermi National Accelerator Laboratory DUNE LBNF from FNAL to Sanford Underground Research Facility, Lead, South Dakota.

BNL Center for Functional Nanomaterials.

BNL National Synchrotron Light Source II.

BNL NSLS II.

BNL Relative Heavy Ion Collider Campus.

BNL RHIC’s newly enhanced STAR detector.

BNL/RHIC Phenix detector.

Brookhaven sPhenix Assembly

BNL RHIC Schematic view of the proposed sPHENIX detector.

BNL RHIC inner hadronic calorimeter being installed in the sPHENIX Detector.

From The DOE’s Brookhaven National Laboratory: “What Triggers Flow Fluctuations in Heavy-Ion Collision Debris?”

From The DOE’s Brookhaven National Laboratory

12.19.22
Karen McNulty Walsh
kmcnulty@bnl.gov
(631) 344-8350

Peter Genzer
genzer@bnl.gov
(631) 344-3174

Comprehensive study pointing to initial state influences on particle flow patterns will help nuclear physicists zero in on key properties of matter that mimics the early universe.

A comprehensive analysis of data from the STAR detector at the Relativistic Heavy Ion Collider (RHIC) [above], reveals that conditions created just as heavy ions collide in the center of the detector have the biggest influence on the asymmetric flow of particles from these collisions. The results will help scientists zero in on key properties of a unique form of matter that mimics the early universe.

Scientists in the STAR [below] collaboration at the Relativistic Heavy Ion Collider [below]—an atom smasher at the U.S. Department of Energy’s Brookhaven National Laboratory—have published a comprehensive analysis aimed at determining which factors most influence fluctuations in the flow of particles from heavy ion collisions. The results, published in Physical Review Letters [below], will help the scientists zero in on key properties of a unique form of matter that mimics the early universe.

The matter these physicists are interested in is called a quark-gluon plasma (QGP)—a trillion-degree soup of quarks and gluons. These are the most fundamental building blocks of all visible matter, the components that make up the protons and neutrons of atomic nuclei. RHIC creates this hot quark soup by colliding beams of large nuclei (a.k.a. heavy ions). The collisions melt the boundaries of individual protons and neutrons so scientists can study the quarks and gluons as they existed nearly 14 billion years ago, before those familiar nuclear particles formed.

“Having a facility that can vary the beam energy and collide different kinds of ions allows us to change the temperature and the density of the hot blob of quark matter, along with its size,” said Niseem Magdy, a postdoctoral fellow at the University of Illinois-Chicago who is one of the leaders of the new analysis. “Studying what happens under those different conditions can tell us more about the properties of the matter we’ve created: how viscous and how flowing it is and how it transforms from one phase to another—from regular nuclei to quark-gluon plasma.”

Go with the flow

For this analysis, the scientists were particularly interested in the asymmetric flow of debris from particle smashups at RHIC. Nuclear physicists have observed from RHIC’s earliest days that off-center collisions preferentially push more particles out along the reaction plane of the colliding nuclei than perpendicular to it. These elliptic flow patterns were important to the discovery that the QGP behaves as liquid with remarkably low viscosity, rather than a uniformly expanding gas.

But the flow is not quite as smooth as that simplistic picture suggests. There are lots of fluctuations. Nailing down the source or sources of those fluctuations will allow the scientists to calculate the plasma’s properties, including its viscosity, much more precisely.

“The fluctuations could come from the initial state, when the ions first collide, or they could develop while QGP is evolving, or they could develop when the system produces the particles we track in our detector,” said Roy Lacey, a professor in the Chemistry and Physics departments at Stony Brook University who served as Magdy’s Ph.D. thesis advisor and guided his work. “When you carefully choose the measurements so as to emphasize different aspects of that timeline you can learn where the fluctuations come from.”

Collisions of gold ions melt protons and neutrons to set free their component particles, quarks and gluons. A new analysis reveals that the conditions set up in the earliest stage of these collisions play the greatest role in causing the asymmetric flow of particles from these collisions, with more particles emerging along the reaction plane than perpendicular to it.

Tracking the source(s)

To tease these contributions apart, the scientists studied flow patterns from a wide range of collisions conducted over many years of RHIC operations.

They analyzed flow data from collisions of different sizes and types of nuclei/ions (gold-gold, uranium-uranium, and copper-gold), and included how central or off-center the ions struck one another. This exercise can help the scientists see the influence of initial state effects—the size and shape of the QGP blob created by the overlapping ions.

They also looked at flow patterns in collisions of the same ion system (gold-gold) over a wide range of collision energies. Because higher energy collisions generate stronger pressure gradients than low energy ones, seeing a difference in flow patterns by energy would reveal that the fluctuations emerge as the blob of hot matter evolves.

And they tracked the flow patterns of different species of particles striking the detector from collisions at the same energy and of the same ion type. Seeing differences in this data would indicate that fluctuations emerge as the QGP transitions back into composite particles (hadrons) made of quarks bound together by gluons.

The results showed that flow fluctuations are most dependent on the conditions created at the initial state of the collision.

The strongest influence: how central the collisions are. Off-center collisions create an oblong, football-shaped overlap region, where the pressure gradient is stronger along the short axis of the football than along the long axis. This asymmetric pressure gradient pushes more particles out along the reaction plane than perpendicular to it, as previously observed. But importantly, the new analysis accounts for the “lumpiness” of the collision zone.

“There are a bunch of small balls [individual protons and neutrons] hitting each other randomly,” Magdy said. “Overall, it looks like an ellipse shape, but there is fluctuation around the edges.”

As a result, Lacey explained, “the density distribution of the matter created is a bit lumpy and that lumpiness influences fluctuations in the flow of particles that ultimately emerge.”

The size of the colliding ions also had a modest effect on flow fluctuations, with small nuclei generating larger flow fluctuations than large nuclei.

In contrast, the analyses showed flow patterns that did not vary significantly with collision energy or among the different particle species produced by hadronization.

“This is the first time that we’ve been able to take all this data collected at RHIC—from the beam energy scan and from collisions of different systems—and combine them together to identify the dependence of these fluctuations,” Magdy said.

Implications

Now that the scientists know the initial state conditions are primarily responsible for the flow fluctuations, they’ll be able to reduce a key longstanding uncertainty and make more precise calculations of the quark-gluon plasma’s properties.

“We are now able to put much, much better constraints on the magnitude of these properties, like bulk viscosity, shear viscosity, and so on,” Lacey said.

That precision will help them chart out more precisely how quark matter changes under different conditions of temperature and pressure—a process that’s similar to mapping out the phases of any type of matter such as water.

“The more precise measurements will help tremendously in trying to narrow down whether or not there are phase transitions in nuclear matter and under what conditions,” Lacey said.

Putting tighter constraints on measurements of viscosity, in particular, may also help scientists discover whether there is a so-called critical point in the nuclear phase diagram. That’s a point where the type of phase change from ordinary nuclear matter to QGP itself changes from a “first-order” transition between two distinct states to a second-order transition. Beyond this point, a smooth crossover transition occurs where both hadrons and QGP can coexist. Precision measurements of viscosity will allow the physicists to look for a dip in shear viscosity that’s expected to occur at this point on the map of nuclear phases.

“The measurements now reported do not give that exact information yet, but we will use these new fluctuation constraints combined with model comparisons to move in that direction,” Lacey said.

As Magdy explained it, “This new analysis is challenging the models to provide an explanation that will accommodate this comprehensive set of data so we can gain a better understanding of the properties and evolution of the quark-gluon plasma.”

This research was funded by the DOE Office of Science (NP), the U.S. National Science Foundation, and a range of international organizations and agencies listed in the scientific paper. The STAR team used computing resources at the Scientific Data and Computing Center at Brookhaven Lab, the National Energy Research Scientific Computing Center (NERSC) at DOE’s Lawrence Berkeley National Laboratory, and the Open Science Grid consortium.

Science paper:
Physical Review Letters

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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Brookhaven Campus

One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc. (AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966.

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS).

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

BNL National Synchrotron Light Source.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider (CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, it was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] as the future Electron–ion collider (EIC) in the United States.

Electron-Ion Collider (EIC) at DOE’s Brookhaven National Laboratory to be built inside the tunnel that currently houses the Relativistic Heavy Ion Collider [RHIC].

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Large Hadron Collider(LHC).

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

Iconic view of the European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] ATLAS detector.

It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] near Geneva, Switzerland.

Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .

DOE’s Fermi National Accelerator Laboratory DUNE LBNF from FNAL to Sanford Underground Research Facility, Lead, South Dakota.

BNL Center for Functional Nanomaterials.

BNL National Synchrotron Light Source II.

BNL NSLS II.

BNL Relative Heavy Ion Collider Campus.

BNL RHIC’s newly enhanced STAR detector.

BNL/RHIC Phenix detector.

Brookhaven sPhenix Assembly

BNL RHIC Schematic view of the proposed sPHENIX detector.

BNL RHIC inner hadronic calorimeter being installed in the sPHENIX Detector.

From The DOE’s Brookhaven National Laboratory: “Comparison Suggests Particles of Light May Create Fluid Flow and Data-Theory”

From The DOE’s Brookhaven National Laboratory

12.13.22

Karen McNulty Walsh
kmcnulty@bnl.gov
(631) 344-8350

Peter Genzer
genzer@bnl.gov
(631) 344-3174

Brookhaven Lab theorist Bjoern Schenke’s hydrodynamic calculations match up with data from collisions of photons with atomic nuclei at the Large Hadron Collider’s ATLAS detector, suggesting those collisions create a fluid of “strongly interacting” particles.

Studying “Little Bangs”: exotic collisions probe the size of quark-gluon plasma. https://atlas.cern/updates/briefing/studying-little-bangs

CERN LHC ATLAS schematic. https://www.bnl.gov/atlas/

A new computational analysis by theorists at the U.S. Department of Energy’s Brookhaven National Laboratory and Wayne State University supports the idea that photons (a.k.a. particles of light) colliding with heavy ions can create a fluid of “strongly interacting” particles. In a paper just published in Physical Review Letters [below], they show that calculations describing such a system match up with data collected by the ATLAS detector [below] at Europe’s Large Hadron Collider (LHC) [below].

As the paper explains, the calculations are based on the hydrodynamic particle flow seen in head-on collisions of various types of ions at both the LHC and the Relativistic Heavy Ion Collider (RHIC) [below], a DOE Office of Science user facility for nuclear physics research at Brookhaven Lab.

BNL RHIC. https://www.bnl.gov/rhic/

With only modest changes, these calculations also describe flow patterns seen in near-miss collisions, where photons that form a cloud around the speeding ions collide with the ions in the opposite beam.

“The upshot is that, using the same framework we use to describe lead-lead and proton-lead collisions, we can describe the data of these ultra-peripheral collisions where we have a photon colliding with a lead nucleus,” said Brookhaven Lab theorist Bjoern Schenke, a coauthor of the paper. “That tells you there’s a possibility that, in these photon-ion collisions, we create a small dense strongly interacting medium that is well described by hydrodynamics—just like in the larger systems.”

Fluid signatures

Observations of particles flowing in characteristic ways have been key evidence that the larger collision systems (lead-lead and proton-lead collisions at the LHC; and gold-gold and proton-gold collisions at RHIC) create a nearly perfect fluid. The flow patterns were thought to stem from the enormous pressure gradients created by the large number of strongly interacting particles produced where the colliding ions overlap.

“By smashing these high-energy nuclei together we’re creating such high energy density—compressing the kinetic energy of these guys into such a small space—that this stuff essentially behaves like a fluid,” Schenke said.

Spherical particles (including protons and nuclei) colliding head on are expected to generate a uniform pressure gradient. But partially overlapping collisions generate an oblong, almond-shaped pressure gradient that pushes more high-energy particles out along the short axis than perpendicular to it.

This “elliptic flow” pattern was one of the earliest hints that particle collisions at RHIC could create a quark-gluon plasma, or QGP—a hot soup of the fundamental building blocks that make up the protons and neutrons of nuclei/ions.

An image of the debris left over after the creation of a quark-gluon plasma in the collision of two nuclei at Brookhaven National Laboratory. Image courtesy of Brookhaven National Laboratory.

Scientists were at first surprised by the QGP’s liquid-like behavior. But they later established elliptic flow as a defining feature of QGP, and evidence that the quarks and gluons were still interacting strongly, even when free from confinement within individual protons and neutrons. Later observations of similar flow patterns in collisions of protons with large nuclei, intriguingly suggest that these proton-nucleus collision systems can also create tiny specks of quark-gluon soup.

“Our new paper is about pushing this to even further extremes, looking at collisions between photons and nuclei,” Schenke said.

Changing the projectile

It has long been known that that ultra-peripheral collisions could create photon-nucleus interactions, using the nuclei themselves as the source of the photons. That’s because charged particles accelerated to high energies, like the lead nuclei/ions accelerated at the LHC (and gold ions at RHIC), emit electromagnetic waves—particles of light. So, each accelerated lead ion at the LHC is essentially surrounded by a cloud of photons.

“When two of these ions pass each other very closely without colliding, you can think of one as emitting a photon, which then hits the lead ion going the other way,” Schenke said. “Those events happen a lot; it’s easier for the ions to barely miss than to precisely hit one another!”

This graphic shows the energy density at different times during the hydrodynamic evolution of the matter created in a collision of a lead nucleus (moving to the left) with a photon emitted from the other lead nucleus (moving to the right). Yellow represents the highest energy density and purple the lowest.

ATLAS scientists recently published data [Physical Review C (below)] on intriguing flow-like signals from these photon-nucleus collisions.

“We had to set up special data collection techniques to pick out these unique collisions,” said Blair Seidlitz, a Columbia University physicist who helped set up the ATLAS trigger system for the analysis when he was a graduate student at the University of Colorado-Boulder. “After collecting enough data, we were surprised to find flow-like signals that were similar to those observed in lead-lead and proton-lead collisions, although they were a little smaller.”

Schenke and his collaborators set out to see whether their theoretical calculations could accurately describe the particle flow patterns.

They used the same hydrodynamic calculations that describe the behavior of particles produced in lead-lead and proton-lead collision systems. But they made a few adjustments to account for the “projectile” striking the lead nucleus changing from a proton to a photon.

According to the laws of physics (specifically, quantum electrodynamics), a photon can undergo quantum fluctuations to become another particle with the same quantum numbers. A rho meson, a particle made of a particular combination of a quark and antiquark held together by gluons, is one of the most likely results of those photon fluctuations.

If you think back to the proton—made of three quarks—this two-quark rho particle is just a step down the complexity ladder.

“Instead of having a gluon distribution around three quarks inside a proton, we have the two quarks (quark-antiquark) with a gluon distribution around those to collide with the nucleus,” Schenke said.

Accounting for energy

The calculations also had to account for the big difference in energy in these photon-nucleus collision systems, compared to proton-lead and especially lead-lead.

“The emitted photon that’s colliding with the lead won’t carry the entire momentum of the lead nucleus it came from, but only a tiny fraction of that. So, the collision energy will be much lower,” Schenke said.

That energy difference turned out to be even more important than the change of projectile.

In the most energetic lead-lead or gold-gold heavy ion collisions, the pattern of particles emerging in the plane transverse to the colliding beams generally persists no matter how far you look from the collision point along the beamline (in the longitudinal direction). But when Schenke and collaborators modeled the patterns of particles expected to emerge from lower-energy photon-lead collisions, it became apparent that including the 3D details of the longitudinal direction made a difference. The model showed that the geometry of the particle distributions changes rapidly with increasing longitudinal distance; the particles become “decorrelated.”

“The particles see different pressure gradients depending on their longitudinal position,” Schenke explained.

“So, for these low energy photon-lead collisions, it is important to run a full 3D hydrodynamic model (which is more computationally demanding) because the particle distribution changes more rapidly as you go out in the longitudinal direction,” he said.

When the theorists compared their predictions using this lower-energy, full 3D, hydrodynamic model with the particle flow patterns observed in photon-lead collisions by the ATLAS detector, the data and theory matched up nicely, at least for the most obvious elliptic flow pattern, Schenke said.

Implications and the future

“From this result, it looks like it’s conceivable that, even in photon-heavy ion collisions, we have a strongly interacting fluid that responds to the initial collision geometry, as described by hydrodynamics,” Schenke said. “If the energies and temperatures are high enough,” he added, “there will be a quark-gluon plasma.”

Seidlitz, the ATLAS physicist, commented, “It was very interesting to see these results suggesting the formation of a small droplet of quark-gluon plasma, as well as how this theoretical analysis offers concrete explanations as to why the flow signatures are a bit smaller in photon-lead collisions.”

Additional data to be collected by ATLAS and other experiments at RHIC and the LHC over the next several years will enable more detailed analyses of particles flowing from photon-nucleus collisions. These analyses will help distinguish the hydrodynamic calculation from another possible explanation, in which the flow patterns are not a result of the system’s response to the initial geometry.

In the longer-term future, experiments at an Electron-Ion Collider (EIC) [below], a facility planned to replace RHIC sometime in the next decade at Brookhaven Lab, could provide more definitive conclusions.

Schenke’s theoretical work was funded by the DOE Office of Science (NP). Operations at RHIC, a DOE Office of Science user facility, and planning for the future EIC are also funded by the Office of Science. Brookhaven Lab physicists play many roles in the ATLAS experiment, also funded by the Office of Science (HEP and NP) and the National Science Foundation.

Science papers:
Physical Review Letters
Physical Review C
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Brookhaven Campus

One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc. (AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966.

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS).

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

BNL National Synchrotron Light Source.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider (CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, it was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] as the future Electron–ion collider (EIC) in the United States.

Electron-Ion Collider (EIC) at DOE’s Brookhaven National Laboratory to be built inside the tunnel that currently houses the Relativistic Heavy Ion Collider [RHIC].

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Large Hadron Collider(LHC).

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

Iconic view of the European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] ATLAS detector.

It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] near Geneva, Switzerland.

Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .

DOE’s Fermi National Accelerator Laboratory DUNE LBNF from FNAL to Sanford Underground Research Facility, Lead, South Dakota.

BNL Center for Functional Nanomaterials.

BNL National Synchrotron Light Source II.

BNL NSLS II.

BNL Relative Heavy Ion Collider Campus.

BNL RHIC’s newly enhanced STAR detector.

BNL/RHIC Phenix detector.

Brookhaven sPhenix Assembly

BNL RHIC Schematic view of the proposed sPHENIX detector.

BNL RHIC inner hadronic calorimeter being installed in the sPHENIX Detector.

From ALICE at CERN(CH): “A ten-year journey through the quark–gluon plasma and beyond”

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN].

From ALICE at CERN(CH)

11.9.22

The ALICE collaboration takes stock of its first decade of quantum chromodynamics studies at the Large Hadron Collider

Quantum chromodynamics (QCD) is one of the pillars of the Standard Model of particle physics.

Standard Model of Particle Physics, Quantum Diaries.

It describes the strong interaction – one of the four fundamental forces of nature. This force holds quarks and gluons – collectively known as partons – together in hadrons such as the proton, and protons and neutrons together in atomic nuclei. Two hallmarks of QCD are chiral symmetry breaking and asymptotic freedom. Chiral symmetry breaking explains how quarks generate the masses of hadrons and therefore the vast majority of visible mass in the universe. Asymptotic freedom states that the strong force between quarks and gluons decreases with increasing energy. The discovery of these two QCD effects garnered two Nobel prizes in physics, in 2008 and 2004, respectively.

High-energy collisions of lead nuclei at the Large Hadron Collider (LHC) explore QCD under the most extreme conditions on Earth. These heavy-ion collisions recreate the quark–gluon plasma (QGP): the hottest and densest fluid ever studied in the laboratory. In contrast to normal nuclear matter, the QGP is a state where quarks and gluons are not confined inside hadrons. It is speculated that the universe was in a QGP state around one millionth of a second after the Big Bang.

Different views of a lead–lead collision event recorded by ALICE in 2015. (Image: CERN)

The ALICE experiment was designed to study the QGP at LHC energies. It was operated during LHC Runs 1 and 2, and has carried out a broad range of measurements to characterize the QGP and to study several other aspects of the strong interaction. In a recent review, highlights of which are described below, the ALICE collaboration takes stock of its first decade of QCD studies at the LHC. The results from these studies include a suite of observables that reveal a complex evolution of the near-perfect QGP liquid that emerges in high-temperature QCD. ALICE measurements also demonstrate that charm quarks equilibrate extremely quickly within this liquid, and are able to regenerate QGP-melted “charmonium” particle states. ALICE has extensively mapped the QGP opaqueness with high-energy probes, and has directly observed the QCD dead-cone effect in proton–proton collisions. Surprising QGP-like signatures have also been observed in rare proton–proton and proton–lead collisions. Finally, ALICE measurements of interactions of produced hadrons have also revealed novel features that have broad implications for nuclear physics and astrophysics.

Probing the QGP at various scales

The QGP can be inspected with various levels of spatial and energy resolution (scale) using particles produced in heavy-ion collisions. High-energy quarks and gluons rapidly cross the QGP and interact with it as they evolve to a spray, or “jet”, of partons that eventually form hadrons, or “hadronize”. The interaction with the QGP reduces the jet’s energy and modifies its structure. A jet with an energy of 20 gigaelectronvolts, for example, can probe distances of 0.01 femtometres (1 femtometre is 10-15 metres), well below the roughly 10-fm size of the QGP. The jet modification, known as jet quenching, results in several distinct effects that ALICE has seen, including significant energy loss for jets and a smaller energy loss for beauty quarks compared to charm quarks.

Lower-energy charm quarks also probe the QGP microscopically, and undergo Brownian motion – a random motion famously studied by Albert Einstein. ALICE has provided evidence that these lower-energy charm quarks participate in the thermalization process by which the QGP reaches thermal equilibrium.

Bound states of a heavy quark and its antimatter counterpart, or “quarkonia”, such as the J/ψ (charmonium) and Υ(1S) (bottomonium), are spatially extended particles and have sizes of about 0.2 fm. They therefore probe the QGP at larger scales compared to high-energy partons. The QGP interferes with the quark–antiquark force and suppresses quarkonia production. For quarkonia made up of charm quarks, ALICE has shown that this suppression, which is stronger for more weakly bound states and thus “hierarchical”, is counterbalanced by charm quark–charm antiquark binding.

This recombination effect has been revealed for the first time at the LHC, where about one hundred charm quarks and antiquarks are produced in each head-on lead–lead collision. It constitutes a proof of quark deconfinement, as it implies that quarks can move freely over distances much larger than the hadron size. The hierarchical suppression can be explained assuming a QGP initial temperature roughly four times higher than the temperature at which the transition from ordinary hadronic matter to the QGP can occur (about two trillion degrees kelvin). An assessment of the QGP temperature was also obtained from the ALICE measurement of photons that are radiated by the plasma during its expansion, yielding an average temperature from the entire temporal evolution of the collision of about twice the QGP transition temperature.

Regarding the large-scale spatial evolution of the collision, ALICE has demonstrated that the QGP formed at LHC energies undergoes the most rapid expansion ever observed for a many-body system in the laboratory. The velocities of the particles that fly out of the QGP in a collective flow approach about 70% of the speed of light, and direction-dependent, or “anisotropic”, flow has been observed for almost all measured hadron species, including light nuclei made of two or three protons and neutrons. Small variations seen in some specific flow patterns of hadrons with opposite electric charge are influenced by the huge electromagnetic fields produced in non-head-on heavy-ion collisions.

Calculations based on hydrodynamics, originally conceived to describe liquids at a few hundred degrees kelvin, describe all of the flow observables, and demonstrate that this theoretical framework is a good description of many-body QCD interactions at trillions of degrees kelvin. Such a description is achieved with the crucial inclusion of a small QGP viscosity, which is the smallest ever determined and thus establishes the QGP as the most perfect liquid.

Hadron formation at high temperatures

During the evolution of a heavy-ion collision, the QGP cools below the transition temperature and hadronizes. After this hadronization, the energy density may be large enough to allow for inelastic (hadron-creating) interactions, which change the medium’s “chemical” composition, in terms of particle species. Such interactions cease at the chemical freeze-out temperature, at which the particle composition is fixed. Elastic (non-hadron creating) interactions can still continue, and halt at the kinetic freeze-out temperature, at which the particle momenta are fixed.

ALICE measurements of hadron production over all momenta have provided an extensive mapping of this hadron chemistry, and they show that hadrons with low momentum form by recombination of quarks from the QGP. Theoretical models, in which a hadron “gas” is in chemical equilibrium after the QGP phase, describe the relative abundances of hadron species using only two properties: the chemical freeze-out temperature, which is very close to the transition temperature predicted by QCD, and a “baryochemical potential” of zero within uncertainties, which demonstrates the matter–antimatter symmetry of the QGP produced at the LHC.

In addition, ALICE investigations into the hadron-gas phase indicate that this phase is prolonged, and that the decoupling of particles from the expanding hadron gas is likely to be a continuous process.

What are the limits of QGP formation?

As the number of particles produced in proton–proton collisions increases (blue lines), the more particles containing at least one strange quark are measured (orange to red squares). (Image: CERN)

Studying how observables such as the particle production yields and multi-particle correlations change with multiplicity – the total number of particles produced – for proton–proton and proton–lead collisions provides a means to explore the thresholds required to form a QGP. A suite of ALICE measurements of high-multiplicity proton–proton and proton–lead collisions exhibit features similar to those observed in lead–lead collisions, where these are associated with QGP formation. The effects include the enhancement of yields of particles with strange quarks, the anisotropic flow determined from particle correlations, and the reduction of the yield of the feebly bound charmonium state ψ(2S) in proton–lead collisions. These observations were among the most surprising and unexpected from the first ten years of LHC running.

The ability of the hydrodynamic framework and of theoretical models of a strongly interacting system to describe many of the observed features, even at low multiplicities, suggests that there is no apparent spatial limit to QGP formation. However, alternative models that do not require the presence of a QGP can also explain a limited number of these features. These models challenge the idea of QGP formation, and this might be supported by the fact that jet quenching has not been observed to date in the small proton–lead colliding system. However, such absence could also be caused by the small spatial extent of a possible QGP droplet, which would decrease the jet quenching. Therefore, the quest for the smallest collision system that leads to QGP formation remains open.

Exploring few-body interactions

ALICE investigations of few-body QCD interactions, such as those that take place in proton–proton collisions or in heavy-ion collisions in which the colliding nuclei only graze past each other, have provided a wide range of measurements. Examples include precise measurements showing that in these collisions the formation of hadrons from charm quarks differs from expectations based on electron-collider measurements, and the first direct observation of the dead-cone effect, which consists of a suppression of the gluons radiated by a massive quark in a forward cone around its direction of flight.

Grazing collisions, known as ultra-peripheral collisions, provide a means of exploring the internal structure of nucleons (protons or neutrons) via the emission of a photon from one nucleus that interacts with the other nucleus. ALICE studies of these collisions show clear evidence that the internal structure of nucleons bound in a nucleus is different from that of free protons.

The large data samples of proton–proton and proton–lead collisions recorded by ALICE have allowed studies of the strong interaction between protons and hyperons – unstable particles that contain strange quarks and may be present in the core of neutron stars. ALICE has shown that the interactions between a proton and Lambda, Xi or Omega hyperon are attractive. These interactions may play a part in the stability of the observed large-mass neutron stars. In addition, ALICE measurements of the lifetime and binding energy of hypertriton – an unstable nucleus composed of a proton, a neutron and a Lambda – are the most accurate to date and shed light on the strong interaction that binds hypernuclei together.

The present and future of ALICE

After a major upgrade, the ALICE experiment started to record Run 3 proton–proton collisions in July 2022. The next full-scale data-taking of lead–lead collisions is planned for 2023, with a proposed pilot run expected in late 2022. The upgraded detector will reconstruct particle trajectories much more precisely and record lead–lead collisions at a higher rate. With the resulting, much larger Run 3 and then Run 4 data sets, rare probes of the QGP that were already used in the past decade, such as heavy quarks and jets, will become high-precision tools to study the QGP. ALICE will also continue to use the small colliding systems to investigate, among other things, the smallest QGP droplet that can be formed and the proton’s inner structure.

Besides further smaller-scale but highly innovative upgrades for the next LHC long shutdown, the ALICE collaboration has prepared a proposal for a completely new detector to be operated in the 2030s. The new detector will open up even more new avenues of exploration, including the study of correlations between charm particles, of chiral-symmetry restoration in the QGP, and of the time-evolution of the QGP temperature.

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Meet CERN CH in a variety of places:

Quantum Diaries

Cern Courier (CH)

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ALICE.

LHC

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

CERN LHC underground tunnel and tube.

The LHC magnets surround the beampipe along its 27 km circumference- Image CERN

CERN SixTrack LHC particles.

From The DOE’s Brookhaven National Laboratory: “‘Quark Matter 2022’ New Results from RHIC and LHC—Plus Plans for the Future”

From The DOE’s Brookhaven National Laboratory

May 24, 2022
Karen McNulty Walsh
kmcnulty@bnl.gov

Meeting highlights include detailed descriptions of fundamental matter and explorations of intriguing physics.

Theoretical and experimental physicists from around the world gathered last month at Quark Matter 2022 to discuss new developments in high energy heavy ion physics. The “29th International Conference on Ultrarelativistic Heavy-Ion Collisions” took place April 4-10, 2022, with both in-person talks in Kraków, Poland, and many participants logging in remotely from around the globe.

Highlights included a series of presentations and discussions about the latest findings from heavy ion research facilities—notably the Relativistic Heavy Ion Collider (RHIC) [below] at the U.S. Department of Energy’s Brookhaven National Laboratory and the Large Hadron Collider [below]at the European Center for Nuclear Research (CERN)—as well as future research directions for the field.

During parts of their research runs, RHIC and the LHC collide heavy ions, which are the nuclei of heavy atoms such as gold and lead that have been stripped of their electrons. These highly energetic, nearly light speed head-on collisions generate temperatures more than 250,000 times hotter than the center of the sun and set free the innermost building blocks of the nuclei—the quarks and gluons that make up protons and neutrons.

The resulting nearly-perfect liquid, the “quark-gluon plasma” (QGP), reflects the conditions of the very early universe nearly 14 billion years ago—an era just a microsecond after the Big Bang before protons and neutrons first formed. By tracking particles that stream out of these collisions, scientists can expand their understanding how matter evolved from the hot quark soup into everything made of atoms in the universe today.

“Quark Matter is the major event for physicists in our field,” said Peter Steinberg, a nuclear physicist at Brookhaven Lab who participates in experiments at both RHIC and the LHC and attended the meeting virtually from his home in Brooklyn, New York. “Held approximately every 18 months, it’s where we usually first share and hear about preliminary results, discuss them with our colleagues, and always learn from one another so that we can strengthen our analyses and experimental approaches.”

Theorists also presented their latest studies including analyses and interpretations of data.

“The field of high-energy heavy ion physics has witnessed major advances through close collaborations between theory and experiment,” said Haiyan Gao, Associate Laboratory Director (ALD) for Nuclear and Particle Physics (NPP) at Brookhaven Lab. “This interplay of theory and experiment is essential to advancing our understanding of how quarks and gluons interact to build of the properties and structure of the matter that makes up our world.”

In addition, several presentations highlighted how results from (and improvements to) heavy-ion experiments at RHIC and the LHC, as well as new theoretical approaches, are paving the way for exciting results to come. That future includes the start of Run 3 at the LHC, installation of the sPHENIX detector at RHIC for the experimental run starting in 2023, and eventually the Electron-Ion Collider (EIC) [below], a brand-new nuclear physics research facility in the preliminary design stage at Brookhaven that is expected to come online early in the next decade.

As is customary for Quark Matter meetings, the day prior to the start of the detailed scientific presentations was dedicated to welcoming students to the field of heavy-ion physics.

“Talks covering the history and goals of heavy ion physics during the student day are designed to encourage undergraduates and graduate students to join us,” Steinberg said.

213 students from undergraduate to PhD levels and 115 early-career postdoctoral fellows registered for the student day, representing institutions in Europe, Asia, North America, South America, and more. Approximately 20 percent of the total were female, with slightly higher female representation (23 percent) in the student group.

“Projects like RHIC and the LHC and the future EIC have been designed from the start as truly international endeavors, seeking to serve the worldwide nuclear and high-energy physics communities,” said Gao. “It is particularly exciting to see so many young people from different backgrounds eager to learn about our research and potentially become the next generation of leaders for these fields. We also recognize that we still have a long way to go to have a more diverse pipeline in our field.”

Highlights from The STAR detector [below]

Brookhaven Lab physicist Prithwish Tribedy presented the highlights from RHIC’s STAR experiment. These included results from RHIC’s isobar collisions. The isobar collisions were designed to explore the effects of the magnetic field generated by colliding ions.

The first isobar analysis looking for evidence of something called the chiral magnetic effect, released last summer, didn’t turn out as expected. Those results indicated that there might be “background” processes that had not yet been considered. Still, the results presented at QM22 demonstrate a definitive difference in the initial magnetic field strength produced in the two types of collisions analyzed, and provide new background estimates for future analyses. The isobar collisions are also offering insight into how the shape of colliding nuclei might influence how particles emerge from these collisions.

Several STAR results helped elucidate characteristics of the phase transition from hadrons (composite particles made of quarks, such as protons and neutrons) to quark-gluon plasma. Tribedy pointed to results showing how that transition happens at different energies. He also discussed how STAR physicists are using results from RHIC’s Beam Energy Scan (BES) to map out features of the nuclear phase diagram and search for a critical point on that plot of nuclear phases.

New data presented on results from 3.85 GeV giga-electron-volt (GeV) collisions of gold ions with a fixed target are consistent with a model calculation which does not have a critical point. With high-statistics data from BES-II, STAR will really explore the critical behavior in the 3-19.6 GeV energy region.

There were also results tracking rare “hypernuclei,” including the first observation of anti-hyper-hydrogen-4. These nuclei contain particles called hyperons, which have at least one “strange” quark, and thus they offer insight into the properties of neutron stars where strange particles are widely thought to be more abundant than they are in normal matter. New STAR results also confirm that the temperature of the QGP is hotter than the sun, and provide a deeper understanding of its detailed properties.

Tribedy ended by describing how new forward detectors have expanded STAR’s capabilities, noting that these forward upgrades will open paths to study the microstructure of the QGP and enable measurements that will bridge the RHIC and EIC science programs. And he pointed attendees to the many later QM22 talks and posters that would elaborate on the details of the topics he’d introduced.

“The rich and diverse physics programs at STAR come from the versatile machine and detector capabilities at RHIC, and the hard work and intellectual contributions of collaborators and scientists from all over the world,” said Lijuan Ruan, a physicist at Brookhaven and co-spokesperson for STAR.

New PHENIX [below] analyses

RHIC’s PHENIX experiment completed operations in 2016, but members of the collaboration are still actively analyzing its data. At QM22, Sanghoon Lim of Pusan National University presented an overview of the collaboration’s latest results.

Lim summarized a wide range of analyses exploring collisions of different types of ions—from “small” protons, deuterons, and helium ions to larger nuclei such as copper, gold, and uranium. These experiments provide a detailed understanding of how features of the nuclear matter created in collisions (and particle interactions with that medium) change with the size of the system.

The newest results further confirm a wide range of data from both Brookhaven and CERN including a string of successive results from PHENIX showing that QGP can be created even in collisions of small particles with larger nuclei. Low-energy photons (particles of light emitted from the QGP) provide a way to probe the temperature of the medium produced and have shown a smooth transition to hot QGP temperatures in both small and large systems.

QM22 also featured long-awaited measurements of high-energy direct photons emitted from head-on and more peripheral deuteron-gold collisions. These measurements are helping scientists understand how much hadrons created in these small systems are being modified by their interactions with the QGP.

Meanwhile the collisions of large nuclei are providing detailed information about the QGP, such as how jets of particles produced in the collisions lose energy as they traverse it. PHENIX physicists extracted new observations by looking at how the angles between particles that make up a jet are correlated with one another. These analyses allow the scientists to probe how the distribution of particles associated with jets might be modified—for example, “quenched” as they lose energy through their interactions with the QGP.

“We are using a technique to study jets that we have been using since the early days of RHIC, but we are now extracting additional quantities from the data that are also being extracted from jet measurements at the LHC,” said Megan Connors, a PHENIX collaborator from Georgia State University (GSU) who presented these results at QM22. “These additional analyses can further constrain theoretical models and improve our understanding of the jet quenching process.”

In addition, PHENIX presented measurements of heavy quarks to study how quarks of different masses lose energy to the QGP as they get caught up in its flow. Final low-energy photon results were also shown. These results zero in on the temperature of the QGP and its evolution as the QGP expands and cools with higher precision than any previous measurements. Lim noted that PHENIX will continue to analyze data, including from 35 billion gold-gold collision events recorded in 2014 and 2016, to further elucidate these properties. And he pointed to a list of newly published and submitted papers—and detailed QM22 talks—for anyone interested in learning more about these results.

“There is no question that PHENIX measurements will continue to play an important role in our field and impact our understanding from small to large collision systems,” GSU’s Connors said.

Brookhaven ATLAS [below] results of note

ATLAS, one of the detectors at the LHC, presented a wide range of results from lead-lead collisions, covering both well-established diagnostics of the QGP as well as an extensive array of new measurements using photons (particles of light) that are present in the intense electromagnetic fields surrounding the lead ions.

ATLAS released a new set of measurements showing how the QGP responds to different types of particle jets produced in lead-lead collisions. By analyzing these data, scientists are trying to distinguish between quarks that come in different “flavors,” as well as between quark and gluon jets. There were also exciting new results exploring how pairs of back-to-back jets (typically referred to as “dijets”) are affected by traversing the plasma. These new findings were a major update of the very first ATLAS result submitted only weeks after the first lead beams collided in the LHC in 2010.

Timothy Rinn, a Brookhaven Lab postdoctoral associate who presented these results, said, “This result provides new insight into the nature of how jets lose energy, or become ‘quenched,’ in dijet events. Many scientists had developed an explanation for earlier jet quenching data based on the belief that the higher energy jet was formed near the surface, and thus must have suffered much less energy loss, while the lower energy jet traveled through a longer distance in the QGP, losing energy along the way. The recent result suggests that both jets in the event typically experience significant energy loss, and pairs of jets where both have a similar energy are observed much less often than expected. These exciting new results are already of great interest to the theoretical community developing sophisticated models of this phenomenon.”

ATLAS also presented a major new result on the “anomalous magnetic moment” of the tau lepton. This is a measure of how tau particles, the heaviest cousin of the electron, “wobble” in a magnetic field, and is commonly referred to as “g-2.” As with measurements of the g-2 for particles called muons (another electron cousin, studied at both Brookhaven and more recently at Fermi National Accelerator Laboratory), seeing deviations from tau leptons’ predicted g-2 value could be an indication that some yet-to-be-discovered particles—physics “beyond the standard model”—are affecting the results. While the ATLAS measurements so far show no significant difference, the results were based on only a small number of events with large uncertainties. Much more data will be collected in LHC Runs 3 and 4, which could be much more exciting.

Plans for sPHENIX and EIC physics

On the final day of the conference, Brookhaven Lab physicist and co-spokesperson of the sPHENIX collaboration David Morrison gave an overview of “The near- and mid-term future of RHIC, EIC and sPHENIX.” Morrison noted how RHIC is well on its way to achieving goals spelled out in the 2015 Long Range Plan for Nuclear Science. These included completing the Beam Energy Scan to map out the phases of quark matter and probing the properties of QGP at shorter and shorter length scales at both RHIC and the LHC.

Dave Morrison, Brookhaven Lab physicist and co-spokesperson for the sPHENIX collaboration, in front of the sPHENIX detector during an early stage of assembly.

The latter goal will be a central focus of sPHENIX, a detector currently under construction at RHIC with the anticipation of taking its first data early next year. During RHIC’s final three years of operation, before conversion of some of its key components into the EIC begins, sPHENIX will collect and analyze data to make precision measurements of jets of particles and bound quark states with different masses, while recent STAR upgrades continue to provide insight into the detailed properties of the QGP.

As described in other talks at QM22, some of those STAR components have also been contributing to a scientific goal that will be a key feature of the EIC—mapping out the internal distribution of quarks and gluons that make up protons and neutrons. The technique for making those measurements at RHIC uses one proton beam’s upward spin alignment as a frame of reference for tracking particle interactions at a wide range of angles from that reference point.

Other recent advances using particles of light that surround the speeding gold ions at RHIC will help pave the way for the EIC science program. In ultraperipheral collisions, where the gold ions graze by one another without direct ion-to-ion impact, the photons surrounding the ions can interact to produce interesting physics—and also serve as probes of the structure within the nuclear particles. At the EIC, speeding electrons will emit virtual photons for probing the inner components of protons and heavier nuclei.

“At RHIC, we also use these ‘photonuclear’ events to study how quarks and gluons contribute to ‘baryon number’—a quantum number that adds up to one in particles made of three quarks—and how that number is affected when these three-quark particles (including protons and neutrons) interact with matter,” said STAR co-spokesperson Ruan. This analysis was done by Nicole Lewis, a postdoctoral fellow in the STAR group at Brookhaven Lab, whose poster contribution was one of 10 (out of 500) selected to be featured in a flash talk at the conference.

“It is wonderful to see so many new results presented at Quark Matter 2022,” concluded Brookhaven Lab NPP ALD Gao. “It takes an enormous effort to prepare for this meeting—and to run the facilities that produce the data presented there. The thousands of physicists, engineers, and technicians at RHIC, the LHC, and their detectors all deserve our sincere gratitude for making this great science possible.”

RHIC operations are funded by the DOE Office of Science, which runs the machine as a User Facility open to an international community of physicists. Each collaboration receives additional funding from a range of international partners and agencies. Brookhaven’s involvement in research at the LHC and the EIC Project are also funded by the DOE Office of Science.

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Brookhaven Campus

One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5,300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission(US) and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc.(AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966.

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS).

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

BNL National Synchrotron Light Source.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider(CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, It was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] (US) as the future Electron–ion collider (EIC) in the United States.

Brookhaven Lab Electron-Ion Collider (EIC) to be built inside the tunnel that currently houses the RHIC.

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] Large Hadron Collider(LHC).

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] map.

Iconic view of the European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN] ATLAS detector.

It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN] near Geneva, Switzerland.

Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .

DOE’s Fermi National Accelerator Laboratory DUNE LBNF from FNAL to Sanford Underground Research Facility, Lead, South Dakota, USA.

BNL Center for Functional Nanomaterials.

BNL National Synchrotron Light Source II.

BNL NSLS II.

BNL Relative Heavy Ion Collider Campus.

BNL/RHIC Star Detector.

BNL/RHIC Phenix detector.

From The Vienna University of Technology [Technische Universität Wien](AT) : “Studying the Big Bang with Artificial Intelligence”

From The Vienna University of Technology [Technische Universität Wien](AT)

25. January 2022

Contact

Dr. Andreas Ipp
Technische Universität Wien
Institut für Theoretische Physik
+43 1 58801 13635
andreas.ipp@tuwien.ac.at

Can machine learning be used to uncover the secrets of the quark-gluon plasma? Yes – but only with sophisticated new methods.

A quark gluon plasma after the collision of two heavy nuclei .

It could hardly be more complicated: tiny particles whir around wildly with extremely high energy, countless interactions occur in the tangled mess of quantum particles, and this results in a state of matter known as “quark-gluon plasma”. Immediately after the Big Bang, the entire univerhttp://public.web.cern.ch/public/se was in this state; today it is produced by high-energy atomic nucleus collisions, for example at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN].

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN].

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH)[CERN] map.

CERN LHC tube in the tunnel. Credit: Maximilien Brice and Julien Marius Ordan.

SixTRack CERN LHC particles.

Such processes can only be studied using high-performance computers and highly complex computer simulations whose results are difficult to evaluate. Therefore, using artificial intelligence or machine learning for this purpose seems like an obvious idea. Ordinary machine-learning algorithms, however, are not suitable for this task. The mathematical properties of particle physics require a very special structure of neural networks. At TU Wien (Vienna), it has now been shown how neural networks can be successfully used for these challenging tasks in particle physics.

Neural networks

“Simulating a quark-gluon plasma as realistically as possible requires an extremely large amount of computing time,” says Dr. Andreas Ipp from the Institute for Theoretical Physics at TU Wien. “Even the largest supercomputers in the world are overwhelmed by this.” It would therefore be desirable not to calculate every detail precisely, but to recognise and predict certain properties of the plasma with the help of artificial intelligence.

Therefore, neural networks are used, similar to those used for image recognition: Artificial “neurons” are linked together on the computer in a similar way to neurons in the brain – and this creates a network that can recognise, for example, whether or not a cat is visible in a certain picture.

When applying this technique to the quark-gluon plasma, however, there is a serious problem: the quantum fields used to mathematically describe the particles and the forces between them can be represented in various different ways. “This is referred to as gauge symmetries,” says Ipp. “The basic principle behind this is something we are familiar with: if I calibrate a measuring device differently, for example if I use the Kelvin scale instead of the Celsius scale for my thermometer, I get completely different numbers, even though I am describing the same physical state. It’s similar with quantum theories – except that there the permitted changes are mathematically much more complicated.” Mathematical objects that look completely different at first glance may in fact describe the same physical state.

Gauge symmetries built into the structure of the network

“If you don’t take these gauge symmetries into account, you can’t meaningfully interpret the results of the computer simulations,” says Dr. David I. Müller. “Teaching a neural network to figure out these gauge symmetries on its own would be extremely difficult. It is much better to start out by designing the structure of the neural network in such a way that the gauge symmetry is automatically taken into account – so that different representations of the same physical state also produce the same signals in the neural network,” says Müller. “That is exactly what we have now succeeded in doing: We have developed completely new network layers that automatically take gauge invariance into account.” In some test applications, it was shown that these networks can actually learn much better how to deal with the simulation data of the quark-gluon plasma.

“With such neural networks, it becomes possible to make predictions about the system – for example, to estimate what the quark-gluon plasma will look like at a later point in time without really having to calculate every single intermediate step in time in detail,” says Andreas Ipp. “And at the same time, it is ensured that the system only produces results that do not contradict gauge symmetry – in other words, results which make sense at least in principle.”

It will be some time before it is possible to fully simulate atomic core collisions at CERN with such methods, but the new type of neural networks provides a completely new and promising tool for describing physical phenomena for which all other computational methods may never be powerful enough.

Science paper:
Physical Review Letters

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At The Vienna University of Technology [Technische Universität Wien](AT), we have been conducting research, teaching and learning under the motto ‘Technology for people’ for over 200 years. TU Wien has evolved into an open academic institution where discussions can happen, opinions can be voiced and arguments will be heard. Although everyone may have different individual philosophies and approaches to life, the staff, management personnel and students at TU Wien all promote open-mindedness and tolerance.

From Symmetry: “Can light melt atoms into goo?”

From Symmetry

08/24/21
Sarah Charley

Courtesy of Christopher Plumberg

The ATLAS experiment [CH] at European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN]. sees possible evidence of quark-gluon plasma production during collisions between photons and heavy nuclei inside the Large Hadron Collider.

European Organization for Nuclear Research[Organisation européenne pour la recherche nucléaire(CH) ATLAS. Credit CERN SCIENCE PHOTO LIBRARY.

Photons—the massless particles also known as the quanta of light—are having a moment in physics research.

Scientists at the Large Hadron Collider have recently studied how, imbued with enough energy, photons can bounce off of one another like massive particles do. Scientists at the LHC and the DOE’s Brookhaven National Laboratory (US) Relative Heavy Ion Collider (US) have also reported seeing photons colliding and converting that energy into massive particles.

DOE’s Brookhaven National Laboratory(US) RHIC Campus

DOE’s Brookhaven National Laboratory (US) Relative Heavy Ion Collider (US).

The photon’s most recent seemingly impossible feat? Smashing so hard into a lead nucleus that the collision seems to produce the same state of matter that existed moments after the Big Bang.

Simulated quark-gluon plasma formation. Courtesy of Chistopher Plumberg.

“I did not expect that photons could produce a quark-gluon plasma until I actually saw the results,” says theoretical nuclear physicist Jacquelyn Noronha-Hostler, an assistant professor at the University of Illinois -Urbana-Champaign (US).

Scientists at the LHC at CERN and at RHIC at DOE’s Brookhaven National Laboratory (US) have known for years they could produce small amounts of quark-gluon plasma in collisions between heavy ions. But this is the first time scientists have reported possible evidence of quark-gluon plasma in the aftermath of a collision between the nucleus of a heavy ion and a massless particle of light.

The scenario seems unlikely. Unlikely, but not impossible, says ATLAS physicist Dennis Perepelitsa, who is an assistant professor at The University of Colorado-Boulder (US).

“In quantum mechanics, everything that is not forbidden is compulsory,” Perepelitsa says. “If it can happen, it will happen. The question is just how often.”

Collisions between photons and lead nuclei are common inside the LHC. Perepelitsa and his colleagues are the first to examine them to find out whether they ever produce a quark-gluon plasma. Their first round of results indicate the answer could be yes, an insight that might provide a new understanding of fluid dynamics.

Scientists contributing to LHC research from US institutions are funded by the Department of Energy (US) and the National Science Foundation (US).

The Large Light Collider

Perepelitsa and his colleagues on the ATLAS experiment went looking for collisions between photons and nuclei, called photonuclear collisions, in data collected during the lead-ion runs at the LHC. These runs have happened in the few weeks just before the LHC’s winter shutdown each year that the LHC has been in operation.

Lead nuclei are made up of protons and neutrons, which are made up of even smaller fundamental particles called quarks. “You can think of the nucleus like a bag of quarks,” Noronha-Hostler says.

This bag of quarks is held together by gluons, which “glue” small groups of quarks into composite particles called hadrons.

When two lead nuclei collide at high energy inside the LHC, the gluons can lose their grip, causing the protons and neutrons to melt and merge into a quark-gluon plasma. The now-free quarks and gluons pull on each other, holding together as the plasma expands and cools.

Eventually, the quarks cool enough to reform into distinct hadrons. Scientists can reconstruct the production, size and shape of the original quark-gluon plasma based on the number, identities and paths of hadrons that escape into their detectors.

During the lead-ion runs at the LHC, nuclei aren’t the only things colliding. Because they have a positive charge, lead nuclei carry strong electromagnetic fields that grow in intensity as they accelerate. Their electromagnetic fields spit out high-energy photons, which can also collide—a fairly common occurence. “There’s a lot of photons, and the nucleus is big,” Perepelitsa says.

Despite their frequency, no one had ever closely examined the detailed patterns of these kinds of photonuclear collisions at the LHC. For this reason, ATLAS scientists had to develop a specialized trigger that could pick out the photon-zapped lead ions from everything else.

According to Blair Seidlitz, a graduate student at CU Boulder, this was tricky. “People have a lot more experience triggering on lead-lead collisions,” he says.

Luckily, photonuclear collisions have a special asymmetrical shape due to the momentum differences between the tiny photon and the massive lead ion: “It’s like a truck hitting a trash can,” Seidlitz says. “All the debris from the collision will move in the direction of the truck.”

Seidlitz designed a trigger that looked for collisions that generated a small number of particles, had a skewed shape, and saw remnants of the partially obliterated lead ion embedded in special detectors 140 meters away from the collision point.

After collecting and analyzing the data, Seidlitz, Perepelitsa and their colleagues saw a particle-flow signature characteristic of a quark-gluon plasma.

The finding alone is not enough to prove the formation of a quark-gluon plasma, but it’s a first clue. “There are always potential competing explanations, and we need to look for other signatures of quark-gluon plasma that could be there,” Perepelitsa says, “but we haven’t measured them yet.”

If the photonuclear collisions are indeed creating quark-gluon plasma, it could be a kind of quantum trick, Perepelitsa says.

Perepelitsa and his colleagues are dubious that a massless photon could pack a powerful enough punch to melt part of a lead nucleus, which contains 82 protons and 126 neutrons. “It would be like throwing a needle into a bowling ball,” he says.

Instead, he thinks that just before impact, these photons are undergoing a transformation originally predicted by Nobel Laureate Paul Dirac.

A quantum transformation

In 1931, Dirac published a paper predicting a new type of particle. The particle would share the mass of the electron but have the opposite charge [positron]. Also, he predicted, “if it collides with an electron, the two will have a chance of annihilating one another.”

It was the positron, the first predicted particle of antimatter. In 1932, The California Institute of Technology (US) physicist Carl Anderson discovered the particle, and later physicists spotted the annihilation process Dirac had predicted as well.

When matter and antimatter meet, the two particles are destroyed, releasing their energy in the form of a pair of photons.

Scientists also see this process happening in reverse, Noronha-Hostler says. “Two photons can interact and create a quark-antiquark pair.”

Before annihilating, that quark-antiquark pair can bind together to make a hadron.

Perepelitsa and his colleagues suspect that the collisions they’ve observed, in which photons appear to be colliding with lead nuclei and creating a small amount of quark-gluon plasma, are not actually collisions between nuclei and photons. Instead, they’re collisions between nuclei and those tiny, ephemeral hadrons.

This makes more sense, Perepelitsa says, as hadrons are bigger in size than photons and are capable of more substantial interactions. “It’s no longer a needle going into a bowling ball, but more like a bullet.”

The smallest drop

For now, the exact mechanism that may be causing this quark-gluon plasma signature within photonuclear collisions remains a mystery. Whatever is going on, Noronha-Hostler says figuring out these collisions could be an important step in quark-gluon plasma research.

LHC scientists’ usual method of studying the quark-gluon plasma has been to examine crashes between lead nuclei, which create a complex soup of quarks and gluons. “We thought originally that the only way we could produce a quark gluon plasma was two massive nuclei hitting each other,” she says. “And then experimentalists started playing around and running smaller things, like protons. With photonuclear collisions, that’s even smaller.”

If photonuclear collisions are creating quark-gluon plasma, it’s in the form of a tiny droplet composed of a few vaporized protons and neutrons.

Scientists are hoping to study these droplets to learn more about how liquids behave on subatomic scales.

“We’re pushing to the most extremes in fluid dynamics,” Noronha-Hostler says. “Not only do we have something that is moving at the speed of light and at the highest temperatures known to humanity, but it looks like we are going to be able to answer ‘What is the smallest droplet of a liquid?’ No other field can do that.”

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Symmetry is a joint Fermilab/SLAC publication.

From DOE’s Brookhaven National Laboratory(US): “Tantalizing Signs of Phase-change ‘Turbulence’ in RHIC Collisions”

From DOE’s Brookhaven National Laboratory(US)

March 5, 2021
Karen McNulty Walsh
Peter Genzer

Fluctuations in net proton production hint at a possible ‘critical point’ marking a change in the way nuclear matter transforms from one phase to another.

The STAR detector at the U.S. Department of Energy’s Brookhaven National Laboratory.

Physicists studying collisions of gold ions at the Relativistic Heavy Ion Collider (RHIC), a U.S. Department of Energy Office of Science user facility for nuclear physics research at DOE’s Brookhaven National Laboratory, are embarking on a journey through the phases of nuclear matter—the stuff that makes up the nuclei of all the visible matter in our universe. A new analysis of collisions conducted at different energies shows tantalizing signs of a critical point—a change in the way that quarks and gluons-the building blocks of protons and neutrons-transform from one phase to another. The findings, just published by RHIC’s STAR Collaboration in the journal Physical Review Letters, will help physicists map out details of these nuclear phase changes to better understand the evolution of the universe and the conditions in the cores of neutron stars.

“If we are able to discover this critical point, then our map of nuclear phases—the nuclear phase diagram—may find a place in the textbooks, alongside that of water,” said Bedanga Mohanty of India’s National Institute of Science and Research, one of hundreds of physicists collaborating on research at RHIC using the sophisticated STAR detector.

As Mohanty noted, studying nuclear phases is somewhat like learning about the solid, liquid, and gaseous forms of water, and mapping out how the transitions take place depending on conditions like temperature and pressure. But with nuclear matter, you can’t just set a pot on the stove and watch it boil. You need powerful particle accelerators like RHIC to turn up the heat.

As physicists turned the collision energy down at RHIC, they expected to see large event-by-event fluctuations in certain measurements such as net proton production—an effect that’s similar to the turbulence an airplane experiences when entering a bank of clouds—as evidence of a “critical point” in the nuclear phase transition. Higher level statistical analyses of the data, including the skew (kurtosis), revealed tantalizing hints of such fluctuations.

RHIC’s highest collision energies “melt” ordinary nuclear matter (atomic nuclei made of protons and neutrons) to create an exotic phase called a quark-gluon plasma (QGP). Scientists believe the entire universe existed as QGP a fraction of a second after the Big Bang—before it cooled and the quarks bound together (glued by gluons) to form protons, neutrons, and eventually, atomic nuclei. But the tiny drops of QGP created at RHIC measure a mere 10^-13 centimeters across (that’s 0.0000000000001 cm) and they last for only 10^-23 seconds! That makes it incredibly challenging to map out the melting and freezing of the matter that makes up our world.

“Strictly speaking if we don’t identify either the phase boundary or the critical point we really can’t put this [QGP phase] into the textbooks and say that we have a new state of matter,” said Nu Xu, a STAR physicist at DOE’s Lawrence Berkeley National Laboratory.

Tracking phase transitions

To track the transitions, STAR physicists took advantage of the incredible versatility of RHIC to collide gold ions (the nuclei of gold atoms) across a wide range of energies.

Mapping nuclear phase changes is like studying how water changes under different conditions of temperature and pressure (net baryon density for nuclear matter). RHIC’s collisions “melt” protons and neutrons to create quark-gluon plasma (QGP). STAR physicists are exploring collisions at different energies, turning the “knobs” of temperature and baryon density, to look for signs of a “critical point.”

“RHIC is the only facility that can do this, providing beams from 200 billion electron volts (GeV) all the way down to 3 GeV. Nobody can dream of such an excellent machine,” Xu said.

The changes in energy turn the collision temperature up and down and also vary a quantity known as net baryon density that is somewhat analogous to pressure. Looking at data collected during the first phase of RHIC’s “beam energy scan” from 2010 to 2017, STAR physicists tracked particles streaming out at each collision energy. They performed a detailed statistical analysis of the net number of protons produced. A number of theorists had predicted that this quantity would show large event-by-event fluctuations as the critical point is approached.

The reason for the expected fluctuations comes from a theoretical understanding of the force that governs quarks and gluons. That theory, known as quantum chromodynamics, suggests that the transition from normal nuclear matter (“hadronic” protons and neutrons) to QGP can take place in two different ways. At high temperatures, where protons and anti-protons are produced in pairs and the net baryon density is close to zero, physicists have evidence of a smooth crossover between the phases. It’s as if protons gradually melt to form QGP, like butter gradually melting on a counter on a warm day. But at lower energies, they expect what’s called a first-order phase transition—an abrupt change like water boiling at a set temperature as individual molecules escape the pot to become steam. Nuclear theorists predict that in the QGP-to-hadronic-matter phase transition, net proton production should vary dramatically as collisions approach this switchover point.

“At high energy, there is only one phase. The system is more or less invariant, normal,” Xu said. “But when we change from high energy to low energy you also increase the net baryon density and the structure of matter may change as you are going through the phase transition area.

“It’s just like when you ride an airplane and you get into turbulence,” he added. “You see the fluctuation—boom, boom, boom. Then, when you pass the turbulence—the phase of structural changes—you are back to normal into the one-phase structure.”

In the RHIC collision data, the signs of this turbulence are not as apparent as food and drinks bouncing off tray tables in an airplane. STAR physicists had to perform what’s known as “higher order correlation function” statistical analysis of the distributions of particles—looking for more than just the mean and width of the curve representing the data to things like how asymmetrical and skewed that distribution is.

The oscillations they see in these higher orders, particularly the skew (or kurtosis), are reminiscent of another famous phase change observed when transparent liquid carbon dioxide suddenly becomes cloudy when heated, the scientists say. This “critical opalescence” comes from dramatic fluctuations in the density of the CO2—variations in how tightly packed the molecules are.

“In our data, the oscillations signify that something interesting is happening, like the opalescence,” Mohanty said.

Yet despite the tantalizing hints the STAR scientists acknowledge that the range of uncertainty in their measurements is still large. The team hopes to narrow that uncertainty to nail their critical point discovery by analyzing a second set of measurements made from many more collisions during phase II of RHIC’s beam energy scan, from 2019 through 2021.

The entire STAR collaboration was involved in the analysis, Xu notes, with a particular group of physicists—including Xiaofeng Luo (and his student, Yu Zhang), Ashish Pandav, and Toshihiro Nonaka, from China, India, and Japan, respectively—meeting weekly with the U.S. scientists (over many time zones and virtual networks) to discuss and refine the results. The work is also a true collaboration of the experimentalists with nuclear theorists around the world and the accelerator physicists at RHIC. The latter group, in Brookhaven Lab’s Collider-Accelerator Department, devised ways to run RHIC far below its design energy while also maximizing collision rates to enable the collection of the necessary data at low collision energies.

“We are exploring uncharted territory,” Xu said. “This has never been done before. We made lots of efforts to control the environment and make corrections, and we are eagerly awaiting the next round of higher statistical data,” he said.

This study was supported by the DOE Office of Science, the U.S. National Science Foundation, and a wide range of international funding agencies listed in the paper. RHIC operations are funded by the DOE Office of Science. Data analysis was performed using computing resources at the RHIC and ATLAS Computing Facility (RACF) at Brookhaven Lab, the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory, and via the Open Science Grid consortium.

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One of ten national laboratories overseen and primarily funded by the DOE(US) Office of Science, DOE’s Brookhaven National Laboratory(US) conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University(US), the largest academic user of Laboratory facilities, and Battelle(US), a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5,300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission(US) and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University(US) and Battelle Memorial Institute(US). From 1947 to 1998, it was operated by Associated Universities, Inc. (AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology(US) to have a facility near Boston, Massachusettes(US). Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia(US), Cornell(US), Harvard(US), Johns Hopkins(US), MIT, Princeton University(US), University of Pennsylvania(US), University of Rochester(US), and Yale University(US).

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS)

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II [below].

BNL NSLS.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider(CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, It was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] as the future Electron–ion collider (EIC) in the United States.

Electron-Ion Collider (EIC) at BNL, to be built inside the tunnel that currently houses the RHIC.

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 (mission need) from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma[16] and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.
Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.
National Synchrotron Light Source II (NSLS-II), Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years.[19] NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.
Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.
Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University.
Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to ATLAS experiment, one of the four detectors located at the Large Hadron Collider (LHC).

CERN map

Iconic view of the CERN (CH) ATLAS detector.

It is currently operating at CERN near Geneva, Switzerland.

Brookhaven was also responsible for the design of the SNS accumulator ring in partnership with Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

ORNL Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Reactor Neutrino Experiment in China and the Deep Underground Neutrino Experiment at DOE’s Fermi National Accelerator Laboratory(US).

Daya Bay, nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China

FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA.

Brookhaven Campus.

BNL Center for Functional Nanomaterials.

BNL NSLS-II.

BNL NSLS II.

BNL RHIC Campus.

BNL/RHIC Star Detector.

BNL/RHIC Phenix.