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  • richardmitnick 10:10 pm on January 25, 2021 Permalink | Reply
    Tags: "RHIC Run 21- Pushing the Limits at the Lowest Collision Energy", An extraordinary soup of free quarks and gluons-a substance that mimics what the early universe was like some 14 billion years ago., , Beam Energy Scan II (BES-II)- a three-year systematic study of what happens when gold ions-gold atoms stripped of their electrons-collide at various low energies., BNL RHIC, , , , Out of the five energies of BES-II—9.8; 7.3; 5.75; 4.6; and 3.85 billion electron volts-or GeV-this year’s run at 3.85 GeV is the most difficult one., , , , RHIC’s highest collision energies (up to 200 GeV) produce temperatures more than 250000 times hotter than the center of the Sun., The goal for this run is to maximize collision rates at the lowest energy ever achieved at RHIC.   

    From DOE’s Brookhaven National Laboratory: “RHIC Run 21- Pushing the Limits at the Lowest Collision Energy” 

    From DOE’s Brookhaven National Laboratory

    January 25, 2021
    Karen McNulty Walsh,
    kmcnulty@bnl.gov
    (631) 344-8350

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

    Final stage of Beam Energy Scan II will collect low-energy collision data needed to understand the transition of ordinary nuclear matter into a soup of free quarks and gluons.

    1
    Accelerator physicist Chuyu Liu, the run coordinator for this year’s experiments at the Relativistic Heavy Ion Collider (RHIC), in the Main Control Room of the collider-accelerator complex at Brookhaven National Laboratory.

    Accelerator physicists are preparing the Relativistic Heavy Ion Collider (RHIC) [below], a DOE Office of Science user facility for nuclear physics research at DOE’s Brookhaven National Laboratory, for its 21st year of experiments, set to begin on or about February 3, 2021. Instead of producing high-energy particle smashups, the goal for this run is to maximize collision rates at the lowest energy ever achieved at RHIC.

    “Run 21 is the final step of Beam Energy Scan II (BES-II), a three-year systematic study of what happens when gold ions—gold atoms stripped of their electrons—collide at various low energies,” said Brookhaven physicist Lijuan Ruan, co-spokesperson for RHIC’s STAR [below] experiment collaboration.

    Nuclear physicists will examine the BES-II data, along with data from RHIC’s high-energy collisions, to map out how these collisions transform ordinary protons and neutrons into an extraordinary soup of free quarks and gluons—a substance that mimics what the early universe was like some 14 billion years ago. By turning the collision energy down, RHIC physicists can change the temperature and other variables to study how these conditions affect the transition from ordinary matter to early-universe hot quark-and-gluon soup.

    “Out of the five energies of BES-II—9.8, 7.3, 5.75, 4.6, and 3.85 billion electron volts, or GeV—this year’s run at 3.85 GeV is the most difficult one,” said Brookhaven Lab accelerator physicist Chuyu Liu, the run coordinator. That’s because “RHIC’s beams of gold ions are really difficult to hold together at the lowest energy,” he explained.

    In Run 21, the accelerator team will use a variety of innovative components and schemes to maintain the lifetime and intensity of the colliding ion beams under challenging conditions. Read on to learn more about RHIC’s Run 21 science goals and the accelerator features that will make the science possible.

    2
    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.” That’s a set of conditions where the type of transition between ordinary nuclear matter and QGP changes from a smooth crossover observed at RHIC’s highest energies (gradual melting) to an abrupt “first order” phase change that’s more like water boiling in a pot.

    Scanning the transition

    As Ruan explained, the quest to map out the phases of nuclear matter and the transitions between them is somewhat similar to studying how water molecules transform from solid ice to liquid water and gaseous steam at different temperatures and pressures. But nuclear matter is trickier to study.

    “We need a powerful particle collider and sophisticated detector systems to create and study the most extreme forms of nuclear matter,” she said. “Thanks to the incredible versatility of RHIC, we can use the ‘knob’ of collision energy and the intricate particle-tracking capabilities of the STAR detector to conduct this systematic study.”

    RHIC’s highest collision energies (up to 200 GeV) produce temperatures more than 250,000 times hotter than the center of the Sun. Those collisions “melt” the protons and neutrons that make up gold atoms’ nuclei, creating an exotic phase of nuclear matter called a quark-gluon plasma (QGP). In QGP, quarks and gluons are “free” from their ordinary confinement within protons and neutrons, and they flow with virtually no resistance—like a nearly perfect liquid.

    But QGP lasts a mere fraction of a second before “freezing out” to form new particles. RHIC physicists piece together details of how the melting and refreezing happen by taking “snapshots” of the particles that stream out of these collisions.

    By systematically lowering the collision energy, the physicists are looking for signs of a so-called “critical point.” This would be a set of conditions where the type of transition between ordinary nuclear matter and QGP changes from the smooth crossover observed at RHIC’s highest energies (picture butter melting gradually on a counter), to an abrupt “first order” phase change (think of how water boils suddenly at a certain temperature and holds that temperature until all the molecules evaporate).

    “Theorists have predicted that certain key measurements at RHIC will exhibit dramatic event-by-event fluctuations when we approach this critical point,” Ruan said.

    Some RHIC physicists liken these fluctuations to the turbulence an airplane experiences when it moves from smooth air into a bank of clouds and then back out again. Measurements from phase I of RHIC’s Beam Energy Scan (BES-I, with data collected between 2010 and 2017) revealed tantalizing hints of such turbulence. But because collisions are hard to achieve at low energies, the data from BES-I aren’t strong enough to draw definitive conclusions.

    Now, in BES-II, a host of accelerator improvements have been implemented to maximize low-energy collision rates.

    Cooling the ions

    One of the innovations that Chuyu Liu and the other Collider-Accelerator Department (C-AD) physicists managing RHIC operations will take advantage of in Run 21 is a first-of-its-kind beam-cooling system. This Low Energy RHIC electron Cooling (LEReC) system operated at full capacity for the first time in last year’s RHIC run, making it the world’s first implementation of electron cooling in a collider. But it will be even more important for the lowest-of-low collision energies this year.

    3
    A host of accelerator improvements have been implemented to maximize RHIC’s low-energy collision rates. These include a series of components that inject a stream of cool electron bunches into the ion beams in these cooling sections of the two RHIC rings. The cool electrons extract heat to counteract the tendency of RHIC’s ions to spread out, thereby maximizing the chances the ions will collide when the beams cross at the center of RHIC’s STAR detector. (Photo taken 2019.)

    “The longer the beam stays at low energy, the more ‘intra-beam scattering’ and ‘space charge’ effects degrade the beam quality, reducing the number of circulating ions,” said Liu. Simplistic translation: The positively charged ions tend to repel one another. (Remember: The ions are atoms of gold stripped of their electrons, leaving a lot of net positive charge from the 79 protons in the nucleus.) The scattering and the repulsive space charge cause the ions to spread out, essentially heating up the beam as it makes its way around the 2.4-mile-circumference RHIC accelerator. And spread-out ions are less likely to collide.

    “The LEReC system operates somewhat similar to the way the liquid running through your home refrigerator extracts heat to keep your food cool,” said Wolfram Fischer, Associate Chair for Accelerators in C-AD, “but the technology needed to achieve this beam cooling is quite a bit more complicated.”

    A series of components (special lasers and a photocathode gun) produces bunches of relatively cool electrons, which are accelerated to match the bunching and near-light-speed pace of RHIC’s ions. Transfer lines inject the cool electrons into the stream of ion bunches—first in one RHIC ring, then, after making a 180-degree turn, into the other. As the particles mix, the electrons extract heat, effectively squeezing the spread-out ion bunches back together. The warmed-up electron bunches then get dumped and replaced with a new cool batch.

    “To add more flexibility for cooling optimization during this year’s run at RHIC’s lowest energy, where the space-charge effects and beam lifetime degradation are concerns for both the electrons and the ions, we installed a new ‘second harmonic’ radiofrequency (RF) cavity in the electron accelerator,” said Alexei Fedotov, the accelerator physicist who led the LEReC project.

    These cavities generate the radio waves that push the electrons along their path, with the higher (second harmonic) frequency helping to flatten out the longitudinal profile of the electron bunches. “This should help to reduce the space charge effect in the electron beams to achieve better cooling performance at low energy,” Fedotov said.

    “We plan to commission the new electron beam transport line in late January and start cooling ions with the new electron beam setup in early February,” he added.

    More accelerator advances

    Similarly, third-harmonic RF cavities installed in the ion accelerator rings will help to flatten the longitudinal profile of the ion bunches, reducing their peak intensity and space charges, Liu explained. “With that, more bunch intensity can be injected into RHIC to produce higher luminosity—a measure closely tied to collision rates,” he said.

    The accelerator team will also be commissioning a new bunch-by-bunch feedback system to help stabilize the beam for a better lifetime. “This system measures how each ion bunch deviates from the center of the beam pipe, and then applies a proportional correction signal through a component called a kicker to nudge each bunch back to where it should be,” Liu said.

    All this cooling and nudging will counteract the ions’ tendency to spread, which maximizes chances of collisions happening when the two beams cross at the center of STAR.

    “This run will bring together many of the advances we’ve been working on at RHIC to meet the challenging conditions of low-energy collisions,” said Fischer. “STAR would have preferred to test the lowest energy first, but we needed to learn everything possible (and develop the electron cooling system) before we could embark on operation at the most difficult energy.”

    See the full article here .


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    Brookhaven Campus.


    BNL Center for Functional Nanomaterials.

    BNL NSLS-II.


    BNL NSLS II.


    BNL RHIC Campus.

    BNL/RHIC Star Detector.

    BNL/RHIC Phenix.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), 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.

     
  • richardmitnick 4:10 pm on December 23, 2020 Permalink | Reply
    Tags: "Recreating Big Bang matter on Earth", , , BNL RHIC, , , , , , ,   

    From CERN (CH): “Recreating Big Bang matter on Earth” 

    Cern New Bloc

    Cern New Particle Event


    From CERN (CH)

    13 NOVEMBER, 2020 [Just now in social media]
    Ana Lopes

    Our fifth story in the LHC Physics at Ten series looks at how the LHC has recreated and greatly advanced our knowledge of the state of matter that is believed to have existed shortly after the Big Bang.

    1
    Recreating Big Bang matter on Earth at CERN’s LHC.

    2
    Illustration of the history of the universe. About one microsecond (μs) from the Big Bang, protons formed from the quark–gluon plasma. Credit: BICEP2 Collaboration/CERN/NASA.

    The Large Hadron Collider (LHC) at CERN usually collides protons together. It is these proton–proton collisions that led to the discovery of the Higgs boson in 2012.

    CERN CMS Higgs Event May 27, 2012.


    CERN ATLAS Higgs Event
    June 12, 2012.

    But the world’s biggest accelerator was also designed to smash together heavy ions, primarily the nuclei of lead atoms, and it does so every year for about one month. And for at least two good reasons. First, heavy-ion collisions at the LHC recreate in laboratory conditions the plasma of quarks and gluons that is thought to have existed shortly after the Big Bang. Second, the collisions can be used to test and study, at the highest manmade temperatures and densities, fundamental predictions of quantum chromodynamics, the theory of the strong force that binds quarks and gluons together into protons and neutrons and ultimately all atomic nuclei.

    The LHC wasn’t the first machine to recreate Big Bang matter: back in 2000, experiments at the Super Proton Synchrotron at CERN found compelling evidence of the quark–gluon plasma.

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

    About five years later, experiments at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in the US started an era of detailed investigation of the quark–gluon plasma.

    BNL/RHIC.

    However, in the 10 years since it achieved collisions at higher energies than its predecessors, the LHC has taken studies of the quark–gluon plasma to incredible new heights. By producing a hotter, denser and longer-lived quark–gluon plasma as well as a larger number and assortment of particles with which to probe its properties and effects, the LHC has allowed physicists to study the quark–gluon plasma with an unprecedented level of detail. What’s more, the machine has delivered some surprising results along the way, stimulating new theoretical studies of this state of matter.

    Heavy collision course

    When heavy nuclei smash into one another in the LHC, the hundreds of protons and neutrons that make up the nuclei release a large fraction of their energy into a tiny volume, creating a fireball of quarks and gluons.

    3
    First proton-lead collision test at the LHC successful | Symmetry Magazine

    These tiny bits of quark–gluon plasma only exist for fleeting moments, with the individual quarks and gluons, collectively known as partons, quickly forming composite particles and antiparticles that fly out in all directions. By studying the zoo of particles produced in the collisions – before, during and after the plasma is created – researchers can study the plasma from the moment it is produced to the moment it cools down and gives way to a state in which composite particles called hadrons can form. However, the plasma cannot be observed directly. Its presence and properties are deduced from the experimental signatures it leaves on the particles that are produced in the collisions and their comparison with theoretical models.

    Such studies can be divided into two distinct categories. The first kind of study investigates the thousands of particles that emerge from a heavy-ion collision collectively, providing information about the global, macroscopic properties of the quark-gluon plasma. The second kind focuses on various types of particle with large mass or momentum, which are produced more rarely and offer a window into the inner, microscopic workings of the medium.

    At the LHC, these studies are conducted by the collaborations behind all four main LHC experiments: ALICE, ATLAS, CMS and LHCb. Although ALICE was initially specifically designed to investigate the quark–gluon plasma, the other three experiments have also since joined this investigation.

    Global properties

    The LHC has delivered data that has enabled researchers to derive with higher precision than previously achieved several global properties of the medium.

    “If we listen to two different musical instruments with closed eyes, we can distinguish between the instruments even when they are playing the same note. The reason is that a note comes with a set of overtones that give the instrument a unique distinct sound. This is but one example of how simple but powerful overtones are in identifying material properties. Heavy-ion physicists have learnt how to make use of “overtones” in their study of the quark–gluon plasma. The initial stage of a heavy-ion collision produces ripples in the plasma that travel through the medium and excite overtones. Such overtones can be measured by analysing the collective flow of particles that fly out of the plasma and reach the detectors. While previous measurements had revealed only first indications of these overtones, the LHC experiments have mapped them out in detail. Combined with other strides in precision, these data have been used by theorists to characterise the plasma’s properties, such as its temperature, energy density and frictional resistance, which is smaller than that of any other known fluid,” explains Wiedemann.

    These findings have then been supported in multiple ways. For instance, the ALICE collaboration estimated the temperature of the plasma by studying photons that are emitted by the hot fireball. The estimated temperature, about 300 MeV (1 MeV is about 10^10 kelvin), is above the predicted temperature necessary for the plasma to be created (about 160 MeV), and is about 40% higher than the one obtained by the RHIC collider.

    Another example is the estimation of the energy density of the plasma in the initial stage of the collisions. ALICE and CMS obtained a value in the range 12–14 GeV per cubic femtometre (1 femtometre is 10-15 metres), about 2–3 times higher than that determined by RHIC, and again above the predicted energy density needed for the plasma to form (about 1 GeV/fm^3).

    5
    Particle trajectories and energy deposition in the ALICE detector during the last lead–lead collisions of the second LHC run. Credit: CERN)

    Inner workings

    The LHC has supplied not just more particles but also more varied types of particle with which to probe the quark–gluon plasma.

    “Together with state-of-the-art particle detectors that cover more area around the collision points as well as sophisticated methods of identifying and tracking particles, this broad palette has offered unprecedented insight into the inner workings and effects of the quark–gluon plasma.”

    To give a few examples, soon after the LHC started, ATLAS and CMS made the first direct observation of the phenomenon of jet quenching, in which jets of particles formed in the collisions lose energy as they cross the quark–gluon plasma medium. The collaborations found a striking imbalance in the energies of pairs of jets, with one jet almost completely absorbed by the medium.

    Another example concerns heavy quarks. Such particles are excellent probes of the quark–gluon plasma because they are produced in the initial stages of a heavy-ion collision and therefore experience the entire evolution of the plasma. The ALICE collaboration has more recently shown that heavy quarks “feel” the shape and size of the quark–gluon plasma, indicating that even the heaviest quarks move with the medium, which is mostly made of light quarks and gluons.

    The LHC experiments, in particular ALICE and CMS, have also significantly improved our understanding of the hierarchical “melting” in the plasma of bound states of a heavy quark and its antiquark, called quarkonia. The more weakly bound the states are, the more easily they will melt, and as a result the less abundant they will be. CMS was the first to observe this so-called hierarchical suppression for bottomonium states, which consist of a bottom quark and its antiquark. And ALICE revealed that, while the most common form of charmonium states, which are composed of a charm quark and its antiquark, is highly suppressed due to the effect of the plasma, it is also regenerated by the recombination of charm quarks and antiquarks. This recombination phenomenon, observed for the first time at the LHC, provides an important testing ground for theoretical models and phenomenology, which forms a link between the theoretical models and experimental data.

    Surprises in smaller systems

    The LHC data have also revealed unexpected results. For example, the ALICE collaboration showed that the enhanced production of strange hadrons (particles containing at least one strange quark), which is traditionally viewed as a signature of the quark-gluon plasma, arises gradually in proton–proton and proton–lead collisions as the number of particles produced in the collisions, or “multiplicity”, increases.

    Another case in point is the gradual onset of a flow-like feature with the shape of a ridge with increasing multiplicity, which was first observed by CMS in proton–proton and proton–lead collisions. This result was further supported by ALICE and ATLAS observations of the emergence of double-ridge features in proton–lead collisions.

    6
    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 in the graph). Credit: CERN)

    “The LHC data have killed the long-held view that proton–proton collisions produce free-streaming sets of particles while heavy-ion collisions produce a fully developed quark–gluon plasma. And they tell us that in the small proton–proton collision systems there are more physical mechanisms at work than traditionally thought. The new challenge is to understand, within the theory of the strong force, how quark–gluon plasma-like properties emerge gradually with the size of the collision system.”

    These are just examples of how 10 years of the LHC have greatly advanced physicists’ knowledge of the quark–gluon plasma and thus of the early universe. And with data from the machine’s second run still being analysed and more data to come from the next run and the High-Luminosity LHC, the LHC’s successor, an even more detailed understanding of this unique state of matter is bound to emerge, perhaps with new surprises in the mix.

    “The coming decade at the LHC offers many opportunities for further exploration of the quark–gluon plasma,” says Musa. “The expected tenfold increase in the number of lead–lead collisions should both increase the precision of measurements of known probes of the medium and give us access to new probes. In addition, we plan to explore collisions between lighter nuclei, which could cast further light on the nature of the medium.”

    See the full article here.


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    Meet CERN (CH) in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier (CH)

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Maximilien Brice and Julien Marius Ordan.


    SixTRack CERN LHC particles

     
  • richardmitnick 11:36 am on February 1, 2020 Permalink | Reply
    Tags: "Exploring strangeness and the primordial Universe", , , , BNL RHIC, , , ,   

    From University of Arizona via phys.org: “Exploring strangeness and the primordial Universe” 

    From University of Arizona

    via


    phys.org

    January 31, 2020
    Springer

    1
    Credit: CC0 Public Domain

    Physicists believe that in the Universe’s first ten microseconds free quarks and gluons filled all of spacetime, forming a new phase of matter named ‘quark-gluon plasma’ (QGP)*. Experimental and theoretical work at CERN was instrumental in the discovery of this hot soup of primordial matter, which is recreated today in accelerator-based lab experiments. To discover QGP in such experiments, the observation of exotic ‘strange’ quarks is very important. If QGP is created, strangeness is readily produced through collisions between gluons. In analysis published in The European Physical Journal Special Topics, Dr. Johann Rafelski from The University of Arizona, United States, also working at CERN, presents how our understanding of this characteristic strangeness production signature has evolved over the span of his long career.

    Using the style of a ‘personal diary,’ Rafelski firstly reviews and summarises decades of work. Describing leading experimental and theoretical contributions, he recounts how and why strange quarks are produced so efficiently in QGP, and how this behaviour has been exploited for QGP discovery. He also explores strangeness as a tool in the search and discovery of this primordial phase of matter; existent at unimaginably high temperatures and pressures. He then follows the line of research through to the ongoing experimental ultra-high-energy experiments involving head-on collisions between both heavy nuclei and lighter protons, carried out at CERN’s Large Hadron Collider (LHC).

    LHC

    CERN map


    CERN LHC Maximilien Brice and Julien Marius Ordan


    CERN LHC particles

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS

    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    Secondly, Rafelski follows the narrative with a commented set of his own unpublished work, focusing on pioneering theories and QGP discovery. He also includes a selection from the comments of referees offering both criticism and praise for these studies; along with his own present-day perspectives. This review highlights the numerous successes enjoyed by theorists, through decades of tireless effort to explain and understand the primordial QGP. All the same, it shows that many pressing questions remain to be answered. Rafelski continues to contribute to the field through his rich research experience and will undoubtedly inspire new generations of physicists to continue the study of exotic quarks in the primordial Universe.

    See the full article here .

    *No mention of the work carried out at Brookhaven Lab’s Relativistic Heavy Ion Collider [RHIC].

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  • richardmitnick 11:31 am on May 24, 2019 Permalink | Reply
    Tags: "STAR Detector has a New Inner Core", , BNL RHIC, BNL Star detector upgrades, Colliding beams of heavy particles such as the nuclei of gold atoms to recreate the extreme conditions of the early universe., Incorporating advanced readout electronics, Inner Time Projection Chamber, , Shrinking electronics= more snapshots,   

    From Brookhaven National Lab: “STAR Detector has a New Inner Core” 

    From Brookhaven National Lab

    May 23, 2019
    Karen McNulty Walsh
    kmcnulty@bnl.gov

    Upgrade to detector sectors tracking particles close to beamline produces stunning images and precision measurements at the Relativistic Heavy Ion Collider.

    BNL/RHIC

    BNL/RHIC Star Detector

    1
    The STAR detector at the Relativistic Heavy Ion Collider (RHIC) is the size of a small house. It captures snapshots of tracks left by thousands of particles created when two gold ions collide. Upgrades to STAR’s inner core now allow the detector to track even more particles, including those with low momentum and those emerging close to the beamline.

    For scientists tracking the transformation of protons and neutrons—the components of atomic nuclei that make up everything we see in the universe today—into a soup of fundamental building blocks known quark-gluon plasma, more is better. More particle tracks, that is. Thanks to a newly installed upgrade of the STAR detector at the Relativistic Heavy Ion Collider (RHIC), nuclear physicists now have more particle tracks than ever to gain insight into the crucial matter-building transition that ran this process in reverse nearly 14 billion years ago.

    RHIC—a U.S. Department of Energy Office of Science User Facility for nuclear physics research at Brookhaven National Laboratory—collides beams of heavy particles such as the nuclei of gold atoms to recreate the extreme conditions of the early universe, including temperatures more than 250,000 times hotter than the center of the sun. The collisions melt the atoms’ protons and neutrons, momentarily setting free their inner building blocks—quarks and gluons—which last existed as free particles one millionth of a second after the Big Bang. The STAR detector captures tracks of particles emerging from the collisions so nuclear physicists can learn about the quarks and gluons—and the force that binds them into more familiar particles as the hot quark-gluon plasma cools.

    3
    Part of the team installing new sectors for the inner Time Projection Chamber (iTPC) at STAR (l to r): Saehanseul Oh, Prashanth Shanmuganathan, Robert Soja, Bill Struble, Peng Liu, and Rahul Sharma.

    The STAR detector upgrade of the “inner Time Projection Chamber,” or iTPC, was completed just in time for this year’s run of collisions at RHIC. It increases the detector’s ability to capture particles emerging close to the beamline in the “forward” and “rearward” directions, as well as particles with low momentum.

    “With the upgrade of the inner TPC, we can dramatically increase the detector coverage and the total number of particles we can measure in any given event,” said Grazyna Odyniec, group leader of Lawrence Berkeley National Laboratory’s Relativistic Nuclear Collisions group, which was responsible for the construction of original STAR TPC and the mechanical components of the new sectors.

    Shrinking electronics, more snapshots

    One key element of the upgrade was incorporating advanced readout electronics, which have come a long way since STAR’s original TPC was assembled at Berkeley Lab in the late 1990s.

    “Because the readout electronics have gotten much smaller, we now fit many more sensors into the inner sectors,” said Brookhaven Lab physicist Flemming Videbaek, project manager for the upgrade. The electronics also have become much faster. That means the detector can take “snapshots” more frequently to capture more details about individual particles’ paths. More frequent sampling also gives STAR access to particles that were previously lost in the measurements with the detector.

    “We are now able to reconstruct tracks that were simply too short for the detector to see,” said Daniel Cebra, a physicist from the University of California, Davis, and a leader of the iTPC effort. “These shorter tracks come from particles that were either emitted at a low angle—meaning close to the beamline in the direction of the colliding ions—or have a low momentum and are thus curled up as they move through the detector’s the magnetic field.”

    Capturing these low-angle and low-momentum particles will give STAR scientists much more data to work with as they search for signs of the quark-gluon plasma phase transition—the main goal of RHIC’s Beam Energy Scan II.

    Collaborative effort

    Building components for the detector enhancement and getting them assembled in time for the low-energy collisions that started in February was a collaborative effort—and a global one.

    A team from the Instituto de Física da Universidade de São Paulo in Brazil designed the main chips for the new signal-readout electronics, which were incorporated into the final assembly by the Brookhaven Lab STAR electronics group.

    6

    Scientists at Berkeley Lab led by Jim Thomas and Howard Wieman prepared the mechanical parts of the new sectors, including “trimming” the alignment of the aluminum frames to match the design specifications within 50 microns in all dimensions.

    And much of the Berkeley team’s wisdom and methods were instrumental in guiding the assembly of the sectors’ wire components by STAR collaborators in China.

    9

    7
    A side view of particle tracks (left) and hits (right) from a collision in STAR, as recorded by the new iTPC sectors (top) compared to the old sectors (bottom). Notice how the new sectors record more hits per track, especially close to the beamline, as well as tracks at more forward and rearward angles (more to the left and right in this view).

    Each of the iTPC’s 24 particle-tracking sectors contains 1500 thin wires arrayed in three layers that amplify signals, establish a particle-guiding electric field, and control which tracks get recorded at STAR. These wires needed to be mounted with extreme precision to keep the relative distance between the layers the same—within 10 microns, or millionths of a meter.

    “We gained experience by building a small prototype even before the design was finalized, and then when it was, we built a full-size version,” said Qinghua Xu, a physicist at Shandong University, who led the Chinese effort. When they completed the first full prototype in 2017, they sent it to Brookhaven for a test run.

    “For the 2018 run, we replaced one of the old sectors with the new prototype, and confirmed that it worked as expected,” Videbaek said. “That gave us confidence that we were ready to build and install the 23 other sectors.”

    Race against time

    The team at Brookhaven started installing sectors in October 2018, using a crane and a precision installation tool designed by Brookhaven Lab engineer Rahul Sharma and fabricated with help from a team lead by Olga Evdokimov at the University of Illinois, Chicago.

    “It was a bit of a race with time,” Videbaek said. “We installed the last electronics just before Christmas and then, in January, filled the TPC with its argon/methane gas mixture and started taking cosmic data,” he said.

    8
    Mounting 1500 thin wires arrayed in three layers on each of the 24 new iTPC sectors took patience, practice, and precision. (Credit: Shandong University)

    The scientists use cosmic rays (charged particles from outer space)—which come through the roof at a rate of about 150 per second—to calibrate the detector and make sure everything is working.

    When the first low-energy collisions came in February, the STAR team was ready with a fully functioning newly efficient detector.

    “We’re grateful to everyone on the team who helped to make this upgrade a success,” Videbaek said.

    Stay tuned for updates about the science the new iTPC will reveal.

    The iTPC upgrade was funded by the DOE Office of Science (NP) with significant financial contributions from the National Science Foundation of China, the Chinese Ministry of Science and Technology, and Shandong University for work done at Shandong U., the University of Science and Technology of China, and the Shanghai Institute of Applied Physics.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus


    BNL Center for Functional Nanomaterials

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), 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.
    i1

     
  • richardmitnick 11:26 am on May 5, 2019 Permalink | Reply
    Tags: 'Where Does A Proton’s Mass Come From?', 99.8% of the proton’s mass comes from gluons, , Antiquarks, Asymptotic freedom: the particles that mediate this force are known as gluons., , BNL RHIC, , , , , , , , The production of Higgs bosons is dominated by gluon-gluon collisions at the LHC, , The strong interaction is the most powerful interaction in the entire known Universe.   

    From Ethan Siegel: “Ask Ethan: ‘Where Does A Proton’s Mass Come From?'” 

    From Ethan Siegel
    May 4, 2019

    1
    The three valence quarks of a proton contribute to its spin, but so do the gluons, sea quarks and antiquarks, and orbital angular momentum as well. The electrostatic repulsion and the attractive strong nuclear force, in tandem, are what give the proton its size, and the properties of quark mixing are required to explain the suite of free and composite particles in our Universe. (APS/ALAN STONEBRAKER)

    The whole should equal the sum of its parts, but doesn’t. Here’s why.

    The whole is equal to the sum of its constituent parts. That’s how everything works, from galaxies to planets to cities to molecules to atoms. If you take all the components of any system and look at them individually, you can clearly see how they all fit together to add up to the entire system, with nothing missing and nothing left over. The total amount you have is equal to the amounts of all the different parts of it added together.

    So why isn’t that the case for the proton? It’s made of three quarks, but if you add up the quark masses, they not only don’t equal the proton’s mass, they don’t come close. This is the puzzle that Barry Duffey wants us to address, asking:

    “What’s happening inside protons? Why does [its] mass so greatly exceed the combined masses of its constituent quarks and gluons?”

    In order to find out, we have to take a deep look inside.

    2
    The composition of the human body, by atomic number and by mass. The whole of our bodies is equal to the sum of its parts, until you get down to an extremely fundamental level. At that point, we can see that we’re actually more than the sum of our constituent components. (ED UTHMAN, M.D., VIA WEB2.AIRMAIL.NET/UTHMAN (L); WIKIMEDIA COMMONS USER ZHAOCAROL (R))

    There’s a hint that comes just from looking at your own body. If you were to divide yourself up into smaller and smaller bits, you’d find — in terms of mass — the whole was equal to the sum of its parts. Your body’s bones, fat, muscles and organs sum up to an entire human being. Breaking those down further, into cells, still allows you to add them up and recover the same mass you have today.

    Cells can be divided into organelles, organelles are composed of individual molecules, molecules are made of atoms; at each stage, the mass of the whole is no different than that of its parts. But when you break atoms into protons, neutrons and electrons, something interesting happens. At that level, there’s a tiny but noticeable discrepancy: the individual protons, neutrons and electrons are off by right around 1% from an entire human. The difference is real.

    3
    From macroscopic scales down to subatomic ones, the sizes of the fundamental particles play only a small role in determining the sizes of composite structures. Whether the building blocks are truly fundamental and/or point-like particles is still not known. (MAGDALENA KOWALSKA / CERN / ISOLDE TEAM)

    CERN ISOLDE

    Like all known organisms, human beings are carbon-based life forms. Carbon atoms are made up of six protons and six neutrons, but if you look at the mass of a carbon atom, it’s approximately 0.8% lighter than the sum of the individual component particles that make it up. The culprit here is nuclear binding energy; when you have atomic nuclei bound together, their total mass is smaller than the mass of the protons and neutrons that comprise them.

    The way carbon is formed is through the nuclear fusion of hydrogen into helium and then helium into carbon; the energy released is what powers most types of stars in both their normal and red giant phases. That “lost mass” is where the energy powering stars comes from, thanks to Einstein’s E = mc². As stars burn through their fuel, they produce more tightly-bound nuclei, releasing the energy difference as radiation.

    4
    In between the 2nd and 3rd brightest stars of the constellation Lyra, the blue giant stars Sheliak and Sulafat, the Ring Nebula shines prominently in the night skies. Throughout all phases of a star’s life, including the giant phase, nuclear fusion powers them, with the nuclei becoming more tightly bound and the energy emitted as radiation coming from the transformation of mass into energy via E = mc². (NASA, ESA, DIGITIZED SKY SURVEY 2)

    NASA/ESA Hubble Telescope

    ESO Online Digitized Sky Survey Telescopes

    Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, United States, altitude 1,712 m (5,617 ft)


    Australian Astronomical Observatory, Siding Spring Observatory, near Coonabarabran, New South Wales, Australia, 1.2m UK Schmidt Telescope, Altitude 1,165 m (3,822 ft)


    From http://archive.eso.org/dss/dss

    This is how most types of binding energy work: the reason it’s harder to pull apart multiple things that are bound together is because they released energy when they were joined, and you have to put energy in to free them again. That’s why it’s such a puzzling fact that when you take a look at the particles that make up the proton — the up, up, and down quarks at the heart of them — their combined masses are only 0.2% of the mass of the proton as a whole. But the puzzle has a solution that’s rooted in the nature of the strong force itself.

    The way quarks bind into protons is fundamentally different from all the other forces and interactions we know of. Instead of the force getting stronger when objects get closer, like the gravitational, electric, or magnetic forces, the attractive force goes down to zero when quarks get arbitrarily close. And instead of the force getting weaker when objects get farther away, the force pulling quarks back together gets stronger the farther away they get.

    5
    The internal structure of a proton, with quarks, gluons, and quark spin shown. The nuclear force acts like a spring, with negligible force when unstretched but large, attractive forces when stretched to large distances. (BROOKHAVEN NATIONAL LABORATORY)

    This property of the strong nuclear force is known as asymptotic freedom, and the particles that mediate this force are known as gluons. Somehow, the energy binding the proton together, responsible for the other 99.8% of the proton’s mass, comes from these gluons. The whole of matter, somehow, weighs much, much more than the sum of its parts.

    This might sound like an impossibility at first, as the gluons themselves are massless particles. But you can think of the forces they give rise to as springs: asymptoting to zero when the springs are unstretched, but becoming very large the greater the amount of stretching. In fact, the amount of energy between two quarks whose distance gets too large can become so great that it’s as though additional quark/antiquark pairs exist inside the proton: sea quarks.

    6
    When two protons collide, it isn’t just the quarks making them up that can collide, but the sea quarks, gluons, and beyond that, field interactions. All can provide insights into the spin of the individual components, and allow us to create potentially new particles if high enough energies and luminosities are reached. (CERN / CMS COLLABORATION)

    Those of you familiar with quantum field theory might have the urge to dismiss the gluons and the sea quarks as just being virtual particles: calculational tools used to arrive at the right result. But that’s not true at all, and we’ve demonstrated that with high-energy collisions between either two protons or a proton and another particle, like an electron or photon.

    The collisions performed at the Large Hadron Collider at CERN are perhaps the greatest test of all for the internal structure of the proton. When two protons collide at these ultra-high energies, most of them simply pass by one another, failing to interact. But when two internal, point-like particles collide, we can reconstruct exactly what it was that smashed together by looking at the debris that comes out.

    7
    A Higgs boson event as seen in the Compact Muon Solenoid detector at the Large Hadron Collider. This spectacular collision is 15 orders of magnitude below the Planck energy, but it’s the precision measurements of the detector that allow us to reconstruct what happened back at (and near) the collision point. Theoretically, the Higgs gives mass to the fundamental particles; however, the proton’s mass is not due to the mass of the quarks and gluons that compose it. (CERN / CMS COLLABORATION)

    Under 10% of the collisions occur between two quarks; the overwhelming majority are gluon-gluon collisions, with quark-gluon collisions making up the remainder. Moreover, not every quark-quark collision in protons occurs between either up or down quarks; sometimes a heavier quark is involved.

    Although it might make us uncomfortable, these experiments teach us an important lesson: the particles that we use to model the internal structure of protons are real. In fact, the discovery of the Higgs boson itself was only possible because of this, as the production of Higgs bosons is dominated by gluon-gluon collisions at the LHC. If all we had were the three valence quarks to rely on, we would have seen different rates of production of the Higgs than we did.

    8
    Before the mass of the Higgs boson was known, we could still calculate the expected production rates of Higgs bosons from proton-proton collisions at the LHC. The top channel is clearly production by gluon-gluon collisions. I (E. Siegel) have added the yellow highlighted region to indicate where the Higgs boson was discovered. (CMS COLLABORATION (DORIGO, TOMMASO FOR THE COLLABORATION) ARXIV:0910.3489)

    As always, though, there’s still plenty more to learn. We presently have a solid model of the average gluon density inside a proton, but if we want to know where the gluons are actually more likely to be located, that requires more experimental data, as well as better models to compare the data against. Recent advances by theorists Björn Schenke and Heikki Mäntysaari may be able to provide those much needed models. As Mäntysaari detailed:

    “It is very accurately known how large the average gluon density is inside a proton. What is not known is exactly where the gluons are located inside the proton. We model the gluons as located around the three [valence] quarks. Then we control the amount of fluctuations represented in the model by setting how large the gluon clouds are, and how far apart they are from each other. […] The more fluctuations we have, the more likely this process [producing a J/ψ meson] is to happen.”

    9
    A schematic of the world’s first electron-ion collider (EIC). Adding an electron ring (red) to the Relativistic Heavy Ion Collider (RHIC) at Brookhaven would create the eRHIC: a proposed deep inelastic scattering experiment that could improve our knowledge of the internal structure of the proton significantly. (BROOKHAVEN NATIONAL LABORATORY-CAD ERHIC GROUP)

    The combination of this new theoretical model and the ever-improving LHC data will better enable scientists to understand the internal, fundamental structure of protons, neutrons and nuclei in general, and hence to understand where the mass of the known objects in the Universe comes from. From an experimental point of view, the greatest boon would be a next-generation electron-ion collider, which would enable us to perform deep inelastic scattering experiments to reveal the internal makeup of these particles as never before.

    But there’s another theoretical approach that can take us even farther into the realm of understanding where the proton’s mass comes from: Lattice QCD.

    10
    A better understanding of the internal structure of a proton, including how the “sea” quarks and gluons are distributed, has been achieved through both experimental improvements and new theoretical developments in tandem. (BROOKHAVEN NATIONAL LABORATORY)

    The difficult part with the quantum field theory that describes the strong force — quantum chromodynamics (QCD) — is that the standard approach we take to doing calculations is no good. Typically, we’d look at the effects of particle couplings: the charged quarks exchange a gluon and that mediates the force. They could exchange gluons in a way that creates a particle-antiparticle pair or an additional gluon, and that should be a correction to a simple one-gluon exchange. They could create additional pairs or gluons, which would be higher-order corrections.

    We call this approach taking a perturbative expansion in quantum field theory, with the idea that calculating higher and higher-order contributions will give us a more accurate result.

    11
    Today, Feynman diagrams are used in calculating every fundamental interaction spanning the strong, weak, and electromagnetic forces, including in high-energy and low-temperature/condensed conditions. But this approach, which relies on a perturbative expansion, is only of limited utility for the strong interactions, as this approach diverges, rather than converges, when you add more and more loops for QCD.(DE CARVALHO, VANUILDO S. ET AL. NUCL.PHYS. B875 (2013) 738–756)

    Richard Feynman © Open University

    But this approach, which works so well for quantum electrodynamics (QED), fails spectacularly for QCD. The strong force works differently, and so these corrections get very large very quickly. Adding more terms, instead of converging towards the correct answer, diverges and takes you away from it. Fortunately, there is another way to approach the problem: non-perturbatively, using a technique called Lattice QCD.

    By treating space and time as a grid (or lattice of points) rather than a continuum, where the lattice is arbitrarily large and the spacing is arbitrarily small, you overcome this problem in a clever way. Whereas in standard, perturbative QCD, the continuous nature of space means that you lose the ability to calculate interaction strengths at small distances, the lattice approach means there’s a cutoff at the size of the lattice spacing. Quarks exist at the intersections of grid lines; gluons exist along the links connecting grid points.

    As your computing power increases, you can make the lattice spacing smaller, which improves your calculational accuracy. Over the past three decades, this technique has led to an explosion of solid predictions, including the masses of light nuclei and the reaction rates of fusion under specific temperature and energy conditions. The mass of the proton, from first principles, can now be theoretically predicted to within 2%.

    12
    As computational power and Lattice QCD techniques have improved over time, so has the accuracy to which various quantities about the proton, such as its component spin contributions, can be computed. By reducing the lattice spacing size, which can be done simply by raising the computational power employed, we can better predict the mass of not only the proton, but of all the baryons and mesons. (LABORATOIRE DE PHYSIQUE DE CLERMONT / ETM COLLABORATION)

    It’s true that the individual quarks, whose masses are determined by their coupling to the Higgs boson, cannot even account for 1% of the mass of the proton. Rather, it’s the strong force, described by the interactions between quarks and the gluons that mediate them, that are responsible for practically all of it.

    The strong nuclear force is the most powerful interaction in the entire known Universe. When you go inside a particle like the proton, it’s so powerful that it — not the mass of the proton’s constituent particles — is primarily responsible for the total energy (and therefore mass) of the normal matter in our Universe. Quarks may be point-like, but the proton is huge by comparison: 8.4 × 10^-16 m in diameter. Confining its component particles, which the binding energy of the strong force does, is what’s responsible for 99.8% of the proton’s mass.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 12:50 pm on January 4, 2019 Permalink | Reply
    Tags: BNL RHIC, Nuclear phase diagram, , , , , Star detector,   

    From Brookhaven National Lab: “Startup Time for Ion Collisions Exploring the Phases of Nuclear Matter” 

    From Brookhaven National Lab

    January 4, 2019
    Karen McNulty Walsh
    kmcnulty@bnl.gov
    (631) 344-8350 or

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

    1
    The Relativistic Heavy Ion Collider (RHIC) is actually two accelerators in one. Beams of ions travel around its 2.4-mile-circumference rings in opposite directions at nearly the speed of light, coming into collision at points where the rings cross.

    BNL RHIC Campus

    January 2 marked the startup of the 19th year of physics operations at the Relativistic Heavy Ion Collider (RHIC), a U.S. Department of Energy Office of Science user facility for nuclear physics research at Brookhaven National Laboratory. Physicists will conduct a series of experiments to explore innovative beam-cooling technologies and further map out the conditions created by collisions at various energies. The ultimate goal of nuclear physics is to fully understand the behavior of nuclear matter—the protons and neutrons that make up atomic nuclei and those particles’ constituent building blocks, known as quarks and gluons.

    BNL RHIC Star detector

    2
    The STAR collaboration’s exploration of the “nuclear phase diagram” so far shows signs of a sharp border—a first-order phase transition—between the hadrons that make up ordinary atomic nuclei and the quark-gluon plasma (QGP) of the early universe when the QGP is produced at relatively low energies/temperatures. The data may also suggest a possible critical point, where the type of transition changes from the abrupt, first-order kind to a continuous crossover at higher energies. New data collected during this year’s run will add details to this map of nuclear matter’s phases.

    Many earlier experiments colliding gold ions at different energies at RHIC have provided evidence that energetic collisions create extreme temperatures (trillions of degrees Celsius). These collisions liberate quarks and gluons from their confinement with individual protons and neutrons, creating a hot soup of quarks and gluons that mimics what the early universe looked like before protons, neutrons, or atoms ever formed.

    “The main goal of this run is to turn the collision energy down to explore the low-energy part of the nuclear phase diagram to help pin down the conditions needed to create this quark-gluon plasma,” said Daniel Cebra, a collaborator on the STAR experiment at RHIC. Cebra is taking a sabbatical leave from his position as a professor at the University of California, Davis, to be at Brookhaven to help coordinate the experiments this year.

    STAR is essentially a house-sized digital camera with many different detector systems for tracking the particles created in collisions. Nuclear physicists analyze the mix of particles and characteristics such as their energies and trajectories to learn about the conditions created when ions collide.

    By colliding gold ions at various low energies, including collisions where one beam of gold ions smashes into a fixed target instead of a counter-circulating beam, RHIC physicists will be looking for signs of a so-called “critical point.” This point marks a spot on the nuclear phase diagram—a map of the phases of quarks and gluons under different conditions—where the transition from ordinary matter to free quarks and gluons switches from a smooth one to a sudden phase shift, where both states of matter can coexist.

    STAR gets a wider view

    STAR will have new components in place that will increase its ability to capture the action in these collisions. These include new inner sectors of the Time Projection Chamber (TPC)—the gas-filled chamber particles traverse from their point of origin in the quark-gluon plasma to the sensitive electronics that line the inner and outer walls of a large cylindrical magnet. There will also be a “time of flight” (ToF) wall placed on one of the STAR endcaps, behind the new sectors.

    “The main purpose of these is to enhance STAR’s sensitivity to signatures of the critical point by increasing the acceptance of STAR—essentially the field of view captured in the pictures of the collisions—by about 50 percent,” said James Dunlop, Associate Chair for Nuclear Physics in Brookhaven Lab’s Physics Department.

    “Both of these components have large international contributions,” Dunlop noted. “A large part of the construction of the iTPC sectors was done by STAR’s collaborating institutions in China. The endcap ToF is a prototype of a detector being built for an experiment called Compressed Baryonic Matter (CBM) at the Facility for Antiproton and Ion Research (FAIR) in Germany. The early tests at RHIC will allow CBM to see how well the detector components behave in realistic conditions before it is installed at FAIR while providing both collaborations with necessary equipment for a mutual-benefit physics program,” he said.

    Tests of electron cooling

    3
    A schematic of low-energy electron cooling at RHIC, from right: 1) a section of the existing accelerator that houses the beam pipe carrying heavy ion beams in opposite directions; 2) the direct current (DC) electron gun and other components that will produce and accelerate the bright beams of electrons; 3) the line that will transport and inject cool electrons into the ion beams; and 4) the cooling sections where ions will mix and scatter with electrons, giving up some of their heat, thus leaving the ion beam cooler and more tightly packed.

    Before the collision experiments begin in mid-February, RHIC physicists will be testing a new component of the accelerator designed to maximize collision rates at low energies.

    “RHIC operation at low energies faces multiple challenges, as we know from past experience,” said Chuyu Liu, the RHIC Run Coordinator for Run 19. “The most difficult one is that the tightly bunched ions tend to heat up and spread out as they circulate in the accelerator rings.”

    That makes it less likely that an ion in one beam will strike an ion in the other.

    To counteract this heating/spreading, accelerator physicists at RHIC have added a beamline that brings accelerated “cool” electrons into a section of each RHIC ring to extract heat from the circulating ions. This is very similar to the way the liquid running through your home refrigerator extracts heat to keep your food cool. But instead of chilled ice cream or cold cuts, the result is more tightly packed ion bunches that should result in more collisions when the counter-circulating beams cross.

    Last year, a team led by Alexei Fedotov demonstrated that the electron beam has the basic properties needed for cooling. After a number of upgrades to increase the beam quality and stability further, this year’s goal is to demonstrate that the electron beam can actually cool the gold-ion beam. The aim is to finish fine-tuning the technique so it can be used for the physics program next year.

    Berndt Mueller, Brookhaven’s Associate Laboratory Director for Nuclear and Particle Physics, noted, “This 19th year of operations demonstrates once again how the RHIC team — both accelerator physicists and experimentalists — is continuing to explore innovative technologies and ways to stretch the physics capabilities of the most versatile particle accelerator in the world.”

    See the full article here .


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    Please help promote STEM in your local schools.

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    BNL Campus

    BNL NSLS-II


    BNL NSLS II

    BNL RHIC Campus

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), 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.
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  • richardmitnick 12:02 pm on December 10, 2018 Permalink | Reply
    Tags: , , , BNL RHIC, , , , The “perfect” liquid, This soup of quarks and gluons flows like a liquid with extremely low viscosity   

    From Brookhaven National Lab: “Compelling Evidence for Small Drops of Perfect Fluid” 

    From Brookhaven National Lab

    December 10, 2018

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

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

    1
    If collisions between small projectiles—protons (p), deuterons (d), and helium-3 nuclei (3He)—and gold nuclei (Au) create tiny hot spots of quark-gluon plasma, the pattern of particles picked up by the detector should retain some “memory” of each projectile’s initial shape. Measurements from the PHENIX experiment match these predictions with very strong correlations between the initial geometry and the final flow patterns. Credit: Javier Orjuela Koop, University of Colorado, Boulder

    Nuclear physicists analyzing data from the PHENIX detector [see below] at the Relativistic Heavy Ion Collider (RHIC) [see below]—a U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research at Brookhaven National Laboratory—have published in the journal Nature Physics additional evidence that collisions of miniscule projectiles with gold nuclei create tiny specks of the perfect fluid that filled the early universe.

    Scientists are studying this hot soup made up of quarks and gluons—the building blocks of protons and neutrons—to learn about the fundamental force that holds these particles together in the visible matter that makes up our world today. The ability to create such tiny specks of the primordial soup (known as quark-gluon plasma) was initially unexpected and could offer insight into the essential properties of this remarkable form of matter.

    “This work is the culmination of a series of experiments designed to engineer the shape of the quark-gluon plasma droplets,” said PHENIX collaborator Jamie Nagle of the University of Colorado, Boulder, who helped devise the experimental plan as well as the theoretical simulations the team would use to test their results.

    The PHENIX collaboration’s latest paper includes a comprehensive analysis of collisions between small projectiles (single protons, two-particle deuterons, and three-particle helium-3 nuclei) with large gold nuclei “targets” moving in the opposite direction at nearly the speed of light. The team tracked particles emerging from these collisions, looking for evidence that their flow patterns matched up with the original geometries of the projectiles, as would be expected if the tiny projectiles were indeed creating a perfect liquid quark-gluon plasma.

    “RHIC is the only accelerator in the world where we can perform such a tightly controlled experiment, colliding particles made of one, two, and three components with the same larger nucleus, gold, all at the same energy,” said Nagle.

    Perfect liquid induces flow

    The “perfect” liquid is now a well-established phenomenon in collisions between two gold nuclei at RHIC, where the intense energy of hundreds of colliding protons and neutrons melts the boundaries of these individual particles and allows their constituent quarks and gluons to mingle and interact freely. Measurements at RHIC show that this soup of quarks and gluons flows like a liquid with extremely low viscosity (aka, near-perfection according to the theory of hydrodynamics). The lack of viscosity allows pressure gradients established early in the collision to persist and influence how particles emerging from the collision strike the detector.

    “If such low viscosity conditions and pressure gradients are created in collisions between small projectiles and gold nuclei, the pattern of particles picked up by the detector should retain some ‘memory’ of each projectile’s initial shape—spherical in the case of protons, elliptical for deuterons, and triangular for helium-3 nuclei,” said PHENIX spokesperson Yasuyuki Akiba, a physicist with the RIKEN laboratory in Japan and the RIKEN/Brookhaven Lab Research Center.

    PHENIX analyzed measurements of two different types of particle flow (elliptical and triangular) from all three collision systems and compared them with predictions for what should be expected based on the initial geometry.

    “The latest data—the triangular flow measurements for proton-gold and deuteron-gold collisions newly presented in this paper—complete the picture,” said Julia Velkovska, a deputy spokesperson for PHENIX, who led a team involved in the analysis at Vanderbilt University. “This is a unique combination of observables that allows for decisive model discrimination.”

    “In all six cases, the measurements match the predictions based on the initial geometric shape. We are seeing very strong correlations between initial geometry and final flow patterns, and the best way to explain that is that quark-gluon plasma was created in these small collision systems. This is very compelling evidence,” Velkovska said.

    Comparisons with theory

    The geometric flow patterns are naturally described in the theory of hydrodynamics, when a near-perfect liquid is created. The series of experiments where the geometry of the droplets is controlled by the choice of the projectile was designed to test the hydrodynamics hypothesis and to contrast it with other theoretical models that produce particle correlations that are not related to initial geometry. One such theory emphasizes quantum mechanical interactions—particularly among the abundance of gluons postulated to dominate the internal structure of the accelerated nuclei—as playing a major role in the patterns observed in small-scale collision systems.

    The PHENIX team compared their measured results with two theories based on hydrodynamics that accurately describe the quark-gluon plasma observed in RHIC’s gold-gold collisions, as well as those predicted by the quantum-mechanics-based theory. The PHENIX collaboration found that their data fit best with the quark-gluon plasma descriptions—and don’t match up, particularly for two of the six flow patterns, with the predictions based on the quantum-mechanical gluon interactions.

    The paper also includes a comparison between collisions of gold ions with protons and deuterons that were specifically selected to match the number of particles produced in the collisions. According to the theoretical prediction based on gluon interactions, the particle flow patterns should be identical regardless of the initial geometry.

    “With everything else being equal, we still see greater elliptic flow for deuteron-gold than for proton-gold, which matches more closely with the theory for hydrodynamic flow and shows that the measurements do depend on the initial geometry,” Velkovska said. “This doesn’t mean that the gluon interactions do not exist,” she continued. “That theory is based on solid phenomena in physics that should be there. But based on what we are seeing and our statistical analysis of the agreement between the theory and the data, those interactions are not the dominant source of the final flow patterns.”

    PHENIX is analyzing additional data to determine the temperature reached in the small-scale collisions. If hot enough, those measurements would be further supporting evidence for the formation of quark-gluon plasma.

    The interplay with theory, including competitive explanations, will continue to play out. Berndt Mueller, Brookhaven Lab’s Associate Director for Nuclear and Particle Physics, has called on experimental physicists and theorists to gather to discuss the details at a special workshop to be held in early 2019. “This back-and-forth process of comparison between measurements, predictions, and explanations is an essential step on the path to new discoveries—as the RHIC program has demonstrated throughout its successful 18 years of operation,” he said.

    This work was supported by the DOE Office of Science, and by all the agencies and organizations supporting research at PHENIX.

    See the full article here .


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  • richardmitnick 3:36 pm on February 2, 2018 Permalink | Reply
    Tags: , , , BNL RHIC, Elke-Caroline Aschenauer, , , ,   

    From BNL: Women in STEM- “Elke-Caroline Aschenauer Awarded Prestigious Humboldt Research Award” 

    Brookhaven Lab

    January 31, 2018
    Karen McNulty Walsh
    kmcnulty@bnl.gov
    (631) 344-8350

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

    1
    Elke-Caroline Aschenauer, widely recognized for helping to design and lead experiments in nuclear physics, at the STAR detector of the Relativistic Heavy Ion Collider (RHIC), a particle collider that explores the particles and forces that form the bulk of visible matter in the universe.

    Elke-Caroline Aschenauer, a senior physicist at the U.S. Department of Energy’s Brookhaven National Laboratory, has been awarded a Humboldt Research Award for her contributions to the field of experimental nuclear physics. This prestigious international award—issued by the Alexander von Humboldt Foundation in Bonn, Germany—comes with a prize of €60,000 (more than $70,000 U.S.) and the opportunity to spend up to one year in Germany (not necessarily continuously) to collaborate with researchers at universities and research organizations there.

    “I am very happy to receive this recognition of my work—the many hours sitting in control rooms, taking data, writing code, and much more,” Aschenauer said. “And I am grateful for the opportunity to have extended stays in Germany to work again with colleagues who are not only colleagues but also friends—some of them I have known since we were finishing our Ph.D.s!”

    These relationships, she said, will help to foster or strengthen collaborations among European and U.S. physicists addressing some of the major research aims at Brookhaven Lab’s Relativistic Heavy Ion Collider (RHIC)—a DOE Office of Science user facility for nuclear physics research—as well as among those hoping to build a U.S.-based Electron-Ion Collider (EIC), a proposed facility for which Aschenauer has been a strong proponent.

    “This opportunity will in many ways help us to be in contact with many experts in the field in Germany and the rest of Europe, and it will help promote the EIC and the Cold QCD Physics program at RHIC,” she said.

    QCD, or Quantum Chromodynamics, is the theory that describes how the strong nuclear force binds the fundamental building blocks of visible matter—the stuff that makes up everything we see in the universe, from stars, to planets, to people. RHIC explores QCD by colliding protons, heavy ions, and protons with heavy ions, sometimes recreating the extreme heat and pressure that existed in the early universe, and sometimes using one particle to probe the structure of another nucleus without heating it up (that is, in its “cold” initial state). By giving scientists a deeper understanding of QCD and the strong nuclear force, these experiments will help elucidate how matter is constructed from the smallest scales imaginable to the large-scale structure of the universe today.

    Aschenauer is widely recognized for helping to design and lead various experiments that have explored these fundamental questions, particularly the internal structure of the protons and neutrons that make up atomic nuclei. At Germany’s Deutsches Elektronen-Synchrotron (DESY) laboratory, she was involved in the HERMES experiment taking snapshots of the inside of protons.

    2
    Hermes

    This experiment revealed the first information about the three-dimensional distribution of smaller building blocks called “quarks,” which are held together inside protons by glue-like “gluons,” carriers of the strong nuclear force. She also helped devise ways to measure how these smaller building blocks contribute to the overall “spin” of protons.

    She continued her explorations of nuclear structure at Thomas Jefferson National Accelerator Facility (Jefferson Lab), leading a new experiment for studying gluon structure through the design and approval stages. Since 2009, she has been the leader of the medium-energy physics group at Brookhaven National Laboratory, designing detector components and new measurement techniques for experiments at RHIC.

    In addition to using particle collisions to recreate the conditions of the early universe, RHIC is also the world’s only polarized proton collider for spin physics studies. Spin, or more precisely, intrinsic angular momentum, is a fundamental property of subatomic particles that is somewhat analogous to the spinning of a toy top with a particular orientation. A particle’s spin influences its optical, electrical, and magnetic characteristics; it is essential to technologies such as magnetic resonance imaging (MRI), for example. Yet the origin of spin in a composite particle such as the proton is still not well understood. Experiments in the 1980s revealed that the spins of a proton’s three main constituent quarks account for only about a third of the overall proton spin, setting off a “crisis” among physicists and a worldwide quest to measure other sources of proton spin.

    Aschenauer has been at the forefront of this effort, bringing both an understanding of the underlying theory and designing and performing cutting-edge experiments to explore spin, both in Germany and the U.S. At RHIC, these experiments have revealed an important role for gluons, possibly equal to or more significant than that of the quarks, in establishing proton spin. As an advocate for a future Electron-Ion Collider, Aschenauer has been instrumental in establishing how this machine could be used to make additional measurements to resolve the inner structure of protons, and is helping to translate those ideas into designs for the detector and interaction region that will achieve this goal at an EIC.

    Aschenauer together with members of her group also developed an innovative way to use spin as a tool for probing the “color” interactions among quarks in a way that tests a theoretical concept of nature’s strongest force and paves a way toward mapping protons’ 3D internal structure. This work established the science case for the key measurements taken during the polarized proton run at RHIC in 2017, and also lays the foundation for future experiments at a proposed EIC.

    As noted by Andreas Schäfer of Germany’s University of Regensburg, who nominated Aschenauer for this honor and will serve as her German host, both the “hot” and “cold” QCD communities of physicists support the EIC thanks in large part to the efforts of Aschenauer and her colleagues to showcase the science that could be achieved at such a machine. He noted that the EIC could also have relevance to the physics program at Europe’s Large Hadron Collider (LHC) and possible future European colliders.

    “All European Electron-Ion Collider User Group members would profit from Aschenauer being in Germany for a longer stretch of time,” Schäfer said. “While Regensburg would be the host university, Aschenauer would spend much of her time meeting with other European groups of experimentalists as well as theoreticians,” he added.

    Aschenauer really enjoys this interplay of experiment and theory and turning ideas into experimental reality.

    “I like the combination between coming up with an idea—how to measure something—and helping to build a detector or system to make that measurement. I find that a very interesting challenge. And then also, once you have done that, you get to analyze the data to get a result that pushes the field forward with new knowledge,” she said.

    “I was fortunate to be involved in a lot of innovative measurements in Germany, which then led to follow-up experiments at Jefferson Lab and at RHIC, where we do things with different methods. The opportunities made possible by this award, particularly the chance to work closely with colleagues in Germany, will help build on those earlier experiences and help us refine how we might pursue these ideas further at a future EIC.”

    Berndt Mueller, Brookhaven Lab’s Associate Laboratory Director for Nuclear and Particle Physics, noted, “Elke has been one of the driving forces of the RHIC Spin program over the past decade, which culminated in the discovery that gluons are major contributors to the spin of the proton. In addition, she has established herself as one of the global leaders developing the science program of a proposed future Electron-Ion Collider. The Humboldt Research Award recognizes her outsized contributions to the science of nucleon structure.”

    Aschenauer earned a Ph.D. in physics from the Swiss Federal Institute of Technology (ETH) Zürich in 1994, then accepted a personal postdoctoral fellowship from the European Union to work at the Dutch National Institute for Subatomic Physics and the University of Ghent in Belgium. She joined DESY in Germany as a postdoc in 1997, beginning her research on proton spin at the HERMES experiment, and became a staff scientist there in 2001. After being part of a team that built the ring-imaging Cherenkov (RICH) detector for HERMES, she spent three years as Deputy Spokesperson and Run Coordinator, and then 3.5 years as the spokesperson of the HERMES experiment. In 2006, she moved to Jefferson Lab and was the group leader of the Hall D scientific and technical staff and project leader for the Hall D contribution to the 12 GeV Upgrade Project. She joined Brookhaven as a staff scientist in 2009, received tenure in 2010, and was named a Fellow of the American Physical Society in 2013.

    See the full article here .

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), 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.
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  • richardmitnick 12:54 pm on January 30, 2018 Permalink | Reply
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    From LBNL: “Applying Machine Learning to the Universe’s Mysteries” 

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    Berkeley Lab

    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    1
    The colored lines represent calculated particle tracks from particle collisions occurring within Brookhaven National Laboratory’s STAR detector at the Relativistic Heavy Ion Collider, and an illustration of a digital brain. The yellow-red glow at center shows a hydrodynamic simulation of quark-gluon plasma created in particle collisions. (Credit: Berkeley Lab)

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    Computers can beat chess champions, simulate star explosions, and forecast global climate. We are even teaching them to be infallible problem-solvers and fast learners.

    And now, physicists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and their collaborators have demonstrated that computers are ready to tackle the universe’s greatest mysteries. The team fed thousands of images from simulated high-energy particle collisions to train computer networks to identify important features.

    The researchers programmed powerful arrays known as neural networks to serve as a sort of hivelike digital brain in analyzing and interpreting the images of the simulated particle debris left over from the collisions. During this test run the researchers found that the neural networks had up to a 95 percent success rate in recognizing important features in a sampling of about 18,000 images.

    The study was published Jan. 15 in the journal Nature Communications.

    The researchers programmed powerful arrays known as neural networks to serve as a sort of hivelike digital brain in analyzing and interpreting the images of the simulated particle debris left over from the collisions. During this test run the researchers found that the neural networks had up to a 95 percent success rate in recognizing important features in a sampling of about 18,000 images.

    The next step will be to apply the same machine learning process to actual experimental data.

    Powerful machine learning algorithms allow these networks to improve in their analysis as they process more images. The underlying technology is used in facial recognition and other types of image-based object recognition applications.

    The images used in this study – relevant to particle-collider nuclear physics experiments at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider and CERN’s Large Hadron Collider – recreate the conditions of a subatomic particle “soup,” which is a superhot fluid state known as the quark-gluon plasma believed to exist just millionths of a second after the birth of the universe. Berkeley Lab physicists participate in experiments at both of these sites.

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    CERN/LHC Map

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    CERN LHC particles

    “We are trying to learn about the most important properties of the quark-gluon plasma,” said Xin-Nian Wang, a nuclear physicist in the Nuclear Science Division at Berkeley Lab who is a member of the team. Some of these properties are so short-lived and occur at such tiny scales that they remain shrouded in mystery.

    In experiments, nuclear physicists use particle colliders to smash together heavy nuclei, like gold or lead atoms that are stripped of electrons. These collisions are believed to liberate particles inside the atoms’ nuclei, forming a fleeting, subatomic-scale fireball that breaks down even protons and neutrons into a free-floating form of their typically bound-up building blocks: quarks and gluons.

    3
    The diagram at left, which maps out particle distribution in a simulated high-energy heavy-ion collision, includes details on particle momentum and angles. Thousands of these images were used to train and test a neural network to identify important features in the images. At right, a neural network used the collection of images to created this “importance map” – the lighter colors represent areas that are considered more relevant to identify equation of state for the quark-gluon matter created in particle collisions. (Credit: Berkeley Lab)

    Researchers hope that by learning the precise conditions under which this quark-gluon plasma forms, such as how much energy is packed in, and its temperature and pressure as it transitions into a fluid state, they will gain new insights about its component particles of matter and their properties, and about the universe’s formative stages.

    But exacting measurements of these properties – the so-called “equation of state” involved as matter changes from one phase to another in these collisions – have proven challenging. The initial conditions in the experiments can influence the outcome, so it’s challenging to extract equation-of-state measurements that are independent of these conditions.

    “In the nuclear physics community, the holy grail is to see phase transitions in these high-energy interactions, and then determine the equation of state from the experimental data,” Wang said. “This is the most important property of the quark-gluon plasma we have yet to learn from experiments.”

    Researchers also seek insight about the fundamental forces that govern the interactions between quarks and gluons, what physicists refer to as quantum chromodynamics.

    Long-Gang Pang, the lead author of the latest study and a Berkeley Lab-affiliated postdoctoral researcher at UC Berkeley, said that in 2016, while he was a postdoctoral fellow at the Frankfurt Institute for Advanced Studies, he became interested in the potential for artificial intelligence (AI) to help solve challenging science problems.

    He saw that one form of AI, known as a deep convolutional neural network – with architecture inspired by the image-handling processes in animal brains – appeared to be a good fit for analyzing science-related images.

    “These networks can recognize patterns and evaluate board positions and selected movements in the game of Go,” Pang said. “We thought, ‘If we have some visual scientific data, maybe we can get an abstract concept or valuable physical information from this.’”

    Wang added, “With this type of machine learning, we are trying to identify a certain pattern or correlation of patterns that is a unique signature of the equation of state.” So after training, the network can pinpoint on its own the portions of and correlations in an image, if any exist, that are most relevant to the problem scientists are trying to solve.

    Accumulation of data needed for the analysis can be very computationally intensive, Pang said, and in some cases it took about a full day of computing time to create just one image. When researchers employed an array of GPUs that work in parallel – GPUs are graphics processing units that were first created to enhance video game effects and have since exploded into a variety of uses – they cut that time down to about 20 minutes per image.

    They used computing resources at Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC) in their study, with most of the computing work focused at GPU clusters at GSI in Germany and Central China Normal University in China.

    NERSC Cray XC40 Cori II supercomputer

    LBL NERSC Cray XC30 Edison supercomputer


    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

    NERSC PDSF


    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    A benefit of using sophisticated neural networks, the researchers noted, is that they can identify features that weren’t even sought in the initial experiment, like finding a needle in a haystack when you weren’t even looking for it. And they can extract useful details even from fuzzy images.

    “Even if you have low resolution, you can still get some important information,” Pang said.

    Discussions are already underway to apply the machine learning tools to data from actual heavy-ion collision experiments, and the simulated results should be helpful in training neural networks to interpret the real data.

    “There will be many applications for this in high-energy particle physics,” Wang said, beyond particle-collider experiments.

    Also participating in the study were Kai Zhou, Nan Su, Hannah Petersen, and Horst Stocker from the following institutions: Frankfurt Institute for Advanced Studies, Goethe University, GSI Helmholtzzentrum für Schwerionenforschung (GSI), and Central China Normal University. The work was supported by the U.S Department of Energy’s Office of Science, the National Science Foundation, the Helmholtz Association, GSI, SAMSON AG, Goethe University, the National Natural Science Foundation of China, the Major State Basic Research Development Program in China, and the Helmholtz International Center for the Facility for Antiproton and Ion Research.

    NERSC is DOE Office of Science user facility.

    See the full article here .

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