Tagged: Quark-gluon plasma Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 12:02 pm on December 10, 2018 Permalink | Reply
    Tags: , , , , , , Quark-gluon plasma, 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 .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    BNL Campus

    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

    Advertisements
     
  • richardmitnick 3:37 pm on November 30, 2018 Permalink | Reply
    Tags: A small and specialized team that studies what happens when the LHC stops colliding protons and instead smashes together heavy atomic nuclei like lead, , , , , Heavy-ion researchers seize their moment, , Quark-gluon plasma,   

    From Symmetry: “Heavy-ion researchers seize their moment” 

    Symmetry Mag
    From Symmetry

    11/30/18
    Sarah Charley

    1

    During the short heavy-ion run at the Large Hadron Collider at CERN, every moment counts.

    When physicist Marta Verweij arrived at CERN in early November, one of the first things she did was pull an all-nighter in the control center for the CMS experiment.

    CERN/CMS Detector

    “We didn’t get to sleep until 2 p.m. the following day,” she says.

    Verweij and her colleagues were trouble-shooting an issue with the CMS trigger system, which was letting too much data through and flooding their computing farm.

    “Once we identified the problem, it was obvious,” says Verweij, who is a physics professor with a joint appointment at Vanderbilt University and the RIKEN group at the US Department of Energy’s Brookhaven National Laboratory. “But we had to look through 700 settings before we found it.”

    Normally when the detector encounters a problem in the middle of the night, the shifters inside the control room alert the on-call expert, who looks into it while the rest of the collaboration sleeps. But when Verweij and her team smelled trouble, they ordered pizza and prepared to settle in for the night. That’s because Verweij is part of a small and specialized team that studies what happens when the LHC stops colliding protons and instead smashes together heavy atomic nuclei, like lead. And according to Verweij, every minute counts.

    “We have four weeks to collect all the data we will use for the next three years,” she says. “During this run we work seven days a week and whatever hours needed. When the machine has no beam, like when the accelerator physicists are refilling the ion source, we can sometimes get some sleep.”

    Scientists will use this data to study the properties of a very hot and dense subatomic material called the quark-gluon plasma. When two lead nuclei collide, their 414 protons and neutrons are liquefied and melt into an ultra-hot soup of quarks and gluons. Cosmologists suspect that the entire universe was filled with a quark-gluon plasma moments after the Big Bang, and astronomers theorize that this primordial material might still live in the hearts of neutron stars. For the last 20 years, experiments at CERN and Brookhaven have produced and studied this quark-gluon plasma, but because it is so short-lived, much remains to be discovered.

    BNL/RHIC

    “We still don’t understand how it evolves over time and what its internal structure looks like,” Verweij says. “We know that it’s not homogenous, but we don’t know how quarks move through it.”

    During this heavy-ion run at CERN, scientists are collecting more data than ever before and will be able to thoroughly investigate these tiny droplets of the early universe. As the run approaches its final few days, Verweij and her team are digging in and planning to finish strong, she says.

    “Now it’s really about squeezing the last bits of data from the detector so that the real fun can start: looking for new signatures of this dense plasma and exploring uncharted territories.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 12:54 pm on January 30, 2018 Permalink | Reply
    Tags: , , , , , , , , , Quark-gluon plasma   

    From LBNL: “Applying Machine Learning to the Universe’s Mysteries” 

    Berkeley Logo

    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)

    BNL/RHIC Star Detector

    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.

    BNL RHIC Campus

    BNL/RHIC

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    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 .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 1:25 pm on April 24, 2017 Permalink | Reply
    Tags: , , , New ALICE results show novel phenomena in proton collisions, , , Quark-gluon plasma, Strange quark   

    From ALICE at CERN: “New ALICE results show novel phenomena in proton collisions” 

    CERN
    CERN New Masthead

    CERN ALICE Icon HUGE

    24 Apr 2017.
    Harriet Kim Jarlett

    1
    As the number of particles produced in proton collisions (the blue lines) increase, the more of these so-called strange hadrons are measured (as shown by the orange to red squares in the graph) (Image: ALICE/CERN)

    In a paper published today in Nature Physics , the ALICE collaboration reports that proton collisions sometimes present similar patterns to those observed in the collisions of heavy nuclei. This behaviour was spotted through observation of so-called strange hadrons in certain proton collisions in which a large number of particles are created. Strange hadrons are well-known particles with names such as Kaon, Lambda, Xi and Omega, all containing at least one so-called strange quark. The observed ‘enhanced production of strange particles’ is a familiar feature of quark-gluon plasma, a very hot and dense state of matter that existed just a few millionths of a second after the Big Bang, and is commonly created in collisions of heavy nuclei. But it is the first time ever that such a phenomenon is unambiguously observed in the rare proton collisions in which many particles are created. This result is likely to challenge existing theoretical models that do not predict an increase of strange particles in these events.

    “We are very excited about this discovery,” said Federico Antinori, Spokesperson of the ALICE collaboration. “We are again learning a lot about this primordial state of matter. Being able to isolate the quark-gluon-plasma-like phenomena in a smaller and simpler system, such as the collision between two protons, opens up an entirely new dimension for the study of the properties of the fundamental state that our universe emerged from.”

    The study of the quark-gluon plasma provides a way to investigate the properties of strong interaction, one of the four known fundamental forces, while enhanced strangeness production is a manifestation of this state of matter. The quark-gluon plasma is produced at sufficiently high temperature and energy density, when ordinary matter undergoes a transition to a phase in which quarks and gluons become ‘free’ and are thus no longer confined within hadrons. These conditions can be obtained at the Large Hadron Collider by colliding heavy nuclei at high energy. Strange quarks are heavier than the quarks composing normal matter, and typically harder to produce. But this changes in presence of the high energy density of the quark-gluon plasma, which rebalances the creation of strange quarks relative to non-strange ones. This phenomenon may now have been observed within proton collisions as well.

    In particular, the new results show that the production rate of these strange hadrons increases with the ‘multiplicity’ – the number of particles produced in a given collision – faster than that of other particles generated in the same collision. While the structure of the proton does not include strange quarks, data also show that the higher the number of strange quarks contained in the induced hadron, the stronger is the increase of its production rate. No dependence on the collision energy or the mass of the generated particles is observed, demonstrating that the observed phenomenon is related to the strange quark content of the particles produced. Strangeness production is in practice determined by counting the number of strange particles produced in a given collision, and calculating the ratio of strange to non-strange particles.

    Enhanced strangeness production had been suggested as a possible consequence of quark-gluon plasma formation since the early eighties, and discovered in collisions of nuclei in the nineties by experiments at CERN’s Super Proton Synchrotron.

    CERN Super Proton Synchrotron

    Another possible consequence of the quark gluon plasma formation is a spatial correlation of the final state particles, causing a distinct preferential alignment with the shape of a ridge. Following its detection in heavy-nuclei collisions, the ridge has also been seen in high-multiplicity proton collisions at the Large Hadron Collider, giving the first indication that proton collisions could present heavy-nuclei-like properties. Studying these processes more precisely will be key to better understand the microscopic mechanisms of the quark-gluon plasma and the collective behaviour of particles in small systems.

    The ALICE experiment has been designed to study collisions of heavy nuclei. It also studies proton-proton collisions, which primarily provide reference data for the heavy-nuclei collisions. The reported measurements have been performed with 7 TeV proton collision data from LHC run 1.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Meet CERN in a variety of places:

    CernCourier
    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS
    ATLAS
    CERN/ATLAS detector

    ALICE
    CERN ALICE New

    CMS
    CERN/CMS Detector

    LHCb

    CERN/LHCb

    LHC

    CERN/LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles


    Quantum Diaries

     
  • richardmitnick 12:59 pm on January 13, 2017 Permalink | Reply
    Tags: , , , , Quark-gluon plasma   

    From BNL: “sPHENIX Gets CD0 for Upgrade to Experiment Tracking the Building Blocks of Matter” 

    Brookhaven Lab

    January 13, 2017
    Karen McNulty Walsh
    kmcnulty@bnl.gov

    First step on a path toward a detector with unprecedented capabilities for deciphering how the properties of the hottest matter in the universe emerge from the interactions of its fundamental particles.

    [SEE? THE USA CAN STILL GET IT DONE IN HEP IF WE JUST MAKE THE RIGHT DECISIONS.]

    1
    The solenoid magnet that will form the core of the sPHENIX detector. No image credit.

    The U.S. Department of Energy (DOE) has granted “Critical Decision-Zero” (CD-0) status to the sPHENIX project, a transformation of one of the particle detectors at the Relativistic Heavy Ion Collider (RHIC)—a DOE Office of Science User Facility at Brookhaven National Laboratory—into a research tool with unprecedented precision for tracking subatomic interactions.

    BNL RHIC Campus
    BNL/RHIC
    RHIC a BNL, with map.

    This decision is an important first step in the DOE process for starting new projects, stating that there is a “mission need” for the capabilities described by the proposal.

    “We are very excited that the Department of Energy has recognized the importance of the sPHENIX project,” said Berndt Mueller, Associate Laboratory Director for Nuclear and Particle Physics at Brookhaven. “This upgrade will offer new insight into how the interactions of the smallest building blocks of matter give rise to the remarkable properties of ‘quark-gluon plasma’—a four-trillion-degree soup of fundamental particles that existed in the universe a microsecond after its birth and recreated regularly in particle collisions at RHIC.”

    As Brookhaven Lab physicist Dave Morrison, a co-spokesperson for the sPHENIX collaboration, explained, “sPHENIX will be an essential tool for exploring the quark-gluon plasma, including its ability to flow like a nearly ‘perfect’ liquid. The capabilities we develop and scientific insight we gain will also help us to prepare for the coming research directions in nuclear physics,” he said.

    2
    A schematic of the sPHENIX experiment at BNL. No image credit.

    The sPHENIX project is an upgrade of RHIC’s former PHENIX detector, which completed its data-taking mission in June 2016.

    “We’ll be leveraging scientific and financial investments already made when building RHIC,” said Gunther Roland, a physicist at the Massachusetts Institute of Technology and the other co-spokesperson for sPHENIX. “But at the same time, the transformation will introduce new, state-of-the-art detector systems.”

    With a superconducting solenoid magnet recycled from a physics experiment at DOE’s SLAC National Laboratory at its core, state-of-the-art particle-tracking detectors, and an array of novel high-acceptance calorimeters, sPHENIX will have the speed and precision needed to track and study the details of particle jets, heavy quarks, and rare, high-momentum particles produced in RHIC’s most energetic collisions. These capabilities will allow nuclear physicists to probe properties of the quark-gluon plasma at varying length scales to make connections between the interactions among individual quarks and gluons and the collective behavior of the liquid-like primordial plasma.

    Conceptual studies and R&D are already underway for key components, including the solenoid, calorimeters, and tracking detectors. The CD0 decision—the go-ahead that enables conceptual design and R&D to proceed—will enable these efforts and set sPHENIX on the path toward an exciting physics program starting in 2022.

    Research at RHIC and the sPHENIX project are supported primarily by the DOE Office of Science.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    BNL Campus

    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 2:06 pm on January 6, 2017 Permalink | Reply
    Tags: , Quark-gluon plasma,   

    From BNL: “Theory Provides Roadmap in Quest for Quark Soup ‘Critical Point'” 

    Brookhaven Lab

    January 4, 2017
    Karen McNulty Walsh
    kmcnulty@bnl.gov

    Scientists seek to discover key point in transition from early universe soup of quarks and gluons to matter as we know it.

    1
    The nuclear theorists behind the new analysis: Swagato Mukherjee, Raju Venugopalan, and Yi Yin.

    Thanks to a new development in nuclear physics theory, scientists exploring expanding fireballs that mimic the early universe have new signs to look for as they map out the transition from primordial plasma to matter as we know it. The theory work, described in a paper recently published as an Editor’s Suggestion in Physical Review Letters (PRL), identifies key patterns that would be proof of the existence of a so-called “critical point” in the transition among different phases of nuclear matter. Like the freezing and boiling points that delineate various phases of water—liquid, solid ice, and steam—the points nuclear physicists seek to identify will help them understand fundamental properties of the fabric of our universe.

    Nuclear physicists create the fireballs by colliding ordinary nuclei—made of protons and neutrons—in an “atom smasher” called the Relativistic Heavy Ion Collider (RHIC), a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory.

    BNL RHIC Campus
    BNL/RHIC
    BNL/RHIC

    The subatomic smashups generate temperatures measuring trillions of degrees, hot enough to “melt” the protons and neutrons and release their inner building blocks—quarks and gluons. The collider essentially turns back the clock to recreate the “quark-gluon plasma” (QGP) that existed just after the Big Bang. By tracking the particles that emerge from the fireballs, scientists can learn about nuclear phase transitions—both the melting and how the quarks and gluons “freeze out” as they did at the dawn of time to form the visible matter of today’s world.

    “We want to understand the properties of QGP,” said nuclear theorist Raju Venugopalan, one of the authors on the new paper. “We don’t know how those properties might be used, but 100 years ago, we didn’t know how we’d use the collective properties of electrons, which now form the basis of almost all of our technologies. Back then, electrons were just as exotic as the quarks and gluons are now.”

    Changing phases

    RHIC physicists believe that two different types of phase changes can transform the hot QGP into ordinary protons and neutrons. Importantly, they suspect that the type of change depends on the collision energy, which determines the temperatures generated and how many particles get caught up in the fireball. This is similar to the way water’s freezing and boiling points can change under different conditions of temperature and the density of water molecules, Venugopalan explained.

    In low energy RHIC collisions, scientists suspect that while the change in phase from QGP to ordinary protons/neutrons occurs, both distinct states (QGP and ordinary nuclear matter) coexist—just like bubbles of steam and liquid water coexist at the same temperature in a pot of boiling water. It’s as if the quarks and gluons (or liquid water molecules) have to stop at that temperature and pay a toll before they can gain the energy needed to escape as QGP (or steam).

    In contrast, in higher energy collisions, there is no toll gate at the transition temperature where quarks and gluons must “stop.” Instead they move on a continuous path between the two phases.

    But what happens between these low-energy and high-energy realms? Figuring that out is now one of the major goals of what’s known as the “beam energy scan” at RHIC. By systematically colliding nuclei at a wide range of energies, physicists in RHIC’s STAR collaboration are searching for evidence of a special point on their map of these nuclear phases and the transitions between them—the nuclear phase diagram.

    At this so-called “critical point,” there would be a toll stop, but the cost would be $0, so the quarks and gluons could transition from protons and neutrons to QGP very quickly—almost as if all the water in the pot turned to steam in a single instant. This can actually happen when water reaches its boiling point under high pressure, where the distinction between the liquid and the compressed gas phases blurs to the point of the two being virtually indistinguishable. In the case of QGP, the physicists would expect to see signs of this dramatic effect—patterns in the fluctuations of particles observed striking their detectors—the closer and closer they get to this critical point.

    In experiments already conducted at the intermediate energies, STAR physicists have observed such patterns, which may be signs of the hypothesized critical point. This search will continue with increased precision over a wider range of energies during a second beam energy scan, beginning in 2019. The new theoretical work of Brookhaven physicist Swagato Mukherjee, Venugopalan, and former postdoc Yi Yin (now at MIT)—part of a newly funded Beam Energy Scan Theory (BEST) Topical Collaboration in Nuclear Theory—will provide a roadmap to guide the experimental researchers.

    2
    The STAR collaboration’s exploration of the “nuclear phase diagram” 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.

    BNL/RHIC Star Detector
    BNL/RHIC Star Detector

    Signposts to look for

    Certain characteristics of the patterns that occur during phase changes are universal—no matter whether you are studying water, or quarks and gluons, or magnets. But one key advance of the new theory work was using a different set of universal characteristics to account for the dynamic conditions of the expanding quark-gluon plasma.

    “All the predictions, the way we started looking for a critical point so far, were based on patterns calculated assuming you have a pot boiling on a stove—a somewhat static system,” said Mukherjee. “But QGP is expanding and changing over time. It’s more like water boiling as it flows rapidly through a pipe.”

    To account for the evolving conditions of the QGP in their calculations, the theorists incorporated “dynamic universalities” that were first developed to describe similar pattern formation in the cosmological expansion of the universe itself.

    “These ideas have since been applied to other systems like liquid helium and liquid crystals,” Venugopalan said. “Yin realized that the specific mechanisms of dynamic universality identified in cosmology and condensed matter systems can be applied to the search for the critical point in heavy ion collisions. This paper is the first explicit demonstration of this conjecture.”

    Specifically, the paper predicts exactly what patterns to look for in the data—patterns in how the properties of particles emitted from the collisions are correlated—as the energy of the collisions changes.

    “If the STAR collaboration looks at the data in a particular way and sees these patterns, they can claim without any ambiguity that they have seen a critical point,” Venugopalan said.

    The Beam Energy Scan Theory Collaboration and research at RHIC are supported by the DOE Office of Science.

    Related Links

    Scientific paper: Universal Off-Equilibrium Scaling of Critical Cumulants in the QCD Phase Diagram

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    BNL Campus

    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 2:10 pm on August 4, 2016 Permalink | Reply
    Tags: , , DEIXIS, , Quark-gluon plasma   

    From BNL via DEIXIS: “Early-universe soup” 

    Brookhaven Lab

    1

    DEIXIS

    June 22nd, 2016 [Just now in social media]
    Sarah Webb

    1
    An experimental and theoretical exploration of the quantum chromodynamics (QCD) phase diagram. The matter produced in collisions at the highest energies and the smallest baryon chemical potentials can change from quark-gluon plasma (QGP) to a hadron gas through a smooth crossover. But lower energy collisions can access higher baryon chemical potentials where a first-order phase transition line is thought to exist. The reach of the future DOE Basic Energy Sciences program at RHIC is shown, as are the trajectories on the phase diagram followed by the cooling droplets of QGP produced in collisions with varying energy. The present reach of lattice QCD calculations is illustrated by the yellow band. (Illustration: Swagato Mukherjee, Brookhaven National Laboratory.)

    ORNL’s Titan supercomputer is helping Brookhaven physicists understand the matter that formed microseconds after the Big Bang.

    ORNL Cray Titan Supercomputer
    ORNL Cray Titan Supercomputer

    At the dawn of the universe – just after the Big Bang – all matter was in the form of a hot-flowing soup called quark-gluon plasma, or QGP. Though a few ambitious, atom-smashing experiments have produced transient samples of this extreme phase of matter, researchers still have much to learn about its fundamental behavior.

    Experimental physicists have tried to produce quark-gluon plasma since the 1980s and first reported observing it in 2000. Over the past 45 years, theorists have outlined the equations that govern QGP and many have combined theory and experiment to describe it.

    Large-scale computations have been critical to the theoretical study of QGP’s novel characteristics. As part of a theoretical effort funded by the Department of Energy, Brookhaven National Laboratory’s Swagato Mukherjee and his colleagues are using an allotment of 167 million processor hours from the ASCR Leadership Computing Challenge (ALCC) to better understand QGP. Their findings will help physicists plan the next wave of experiments. “Neither theory nor experiment can do this alone,” Mukherjee says.

    At the heart of every atom lies the nucleus, a super-tight ball of subatomic protons and neutrons. Those particles are made of even smaller parts, including quarks, which comprise just one thousandth of the mass. Gluons, the adhesive particles that hold quarks together, carry the strong interaction, a fundamental physical force that binds the atomic nucleus and generates the other 99.9 percent of all matter’s mass.

    But at temperature extremes 70,000 times hotter than the center of the sun, even tightly packed quarks and gluons begin to flow. The transition to the flowing state is much like phase changes in matter such as water. Water exists as liquid, steam or ice, based on how much heat and pressure are applied. Scientists long ago carefully mapped the underlying conditions and boundaries between water’s different forms as a phase diagram, information that’s been critical for understanding water’s behavior. If researchers can understand how changes in temperature and density affect QGP, physicists can create a similar roadmap documenting conditions that form it.

    Because of the extreme conditions required for QGP creation, the only way to observe it on Earth is to bombard matter with high-energy particles at either the Relativistic Heavy Ion Collider (RHIC) at Brookhaven or the Large Hadron Collider at CERN in Switzerland.

    BNL/RHIC
    BNL/RHIC

    CERN LHC Grand Tunnel
    LHC
    Fast-moving nuclei of lead and gold collide at high energy, briefly producing the plasma-soup researchers can study.

    Experiments aren’t the only way to study QGP’s properties. Physicists have worked out the theory of how quarks and gluons interact, known as quantum chromodynamics, or QCD. However, the complexity of these interactions, with billions of variables, requires sophisticated parallel computing resources to solve, Mukherjee says.

    Using their ALCC allotment, Mukherjee and his colleagues have concentrated on a version of this theory, lattice QCD, to computationally study the plasma on Titan, a Cray XK7 at Oak Ridge National Laboratory. The calculations line up quarks at the intersection points on a grid, with gluons positioned on each of the crossbars between them. Initially, the researchers omitted the density component and solely calculated how increasing heat eventually produces the flowing QGP. Now they’ll need to consider the density component as well. With their ongoing ALCC allotment, they’re simulating how increasing density changes the phase diagram and eventually the plasma’s behavior.

    These types of computations will be critical for future experiments at the big colliders. In 2019 and 2020, DOE will support a large collaborative effort, the Beam Energy Scan II at RHIC, to observe the full phase diagram of quark-gluon plasma, including the density component, Mukherjee says, an effort that will cost hundreds of millions of dollars. The calculations Mukherjee and his colleagues perform will provide information that helps the experimental physicists plan those experiments. The calculations will provide temperature benchmarks – a range needed to generate QGP.

    In large particle accelerators, researchers can’t control the temperature or density, only the energy of the atomic collisions, Mukherjee says. So calculations will help researchers translate that collision energy into the heat and density parameters they need to observe the full range of changes in the phase diagram of quark-gluon plasma.

    Ultimately, the exercise is about fundamental discovery and collaboration between theorists and experimentalists to discover the quark-gluon soup recipe. Mukherjee is part of a larger Brookhaven theoretical team, the Nuclear Physics Lattice Gauge Theory group led by Fritjof Karsch. This work is an integral part of the BEST collaboration – for Beam Energy Scan Theory – a DOE-funded, multi-institutional Topical Collaboration in Nuclear Theory, looking at the phases and properties of hot-dense QCD matter. Mukherjee’s research is supported by DOE Office of Science’s Nuclear Physics program.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    BNL Campus

    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 3:21 pm on April 10, 2016 Permalink | Reply
    Tags: , , , , , , Quark-gluon plasma   

    From The Daily Galaxy: “CERN LHC Reveals: “The Universe a Billionth of a Second After the Big Bang” 

    Daily Galaxy
    The Daily Galaxy

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    April 09, 2016
    No writer credit found

    “It is remarkable that we are able to carry out such detailed measurements on a drop of ‘early universe’, that only has a radius of about one millionth of a billionth of a meter. The results are fully consistent with the physical laws of hydrodynamics, i.e. the theory of flowing liquids and it shows that the quark-gluon plasma behaves like a fluid.

    It is however a very special liquid, as it does not consist of molecules like water, but of the fundamental particles quarks and gluons,” explained Jens Jørgen Gaardhøje, professor and head of the ALICE group at the Niels Bohr Institute at the University of Copenhagen.

    A few billionths of a second after the Big Bang, the universe was made up of a kind of extremely hot and dense primordial soup of the most fundamental particles, especially quarks and gluons. This state is called quark-gluon plasma. By colliding lead nuclei at a record-high energy of 5.02 TeV in the world’s most powerful particle accelerator, the 27 km long Large Hadron Collider, LHC at CERN in Geneva, it has been possible to recreate this state in the ALICE experiment’s detector and measure its properties.

    Quark gluon plasma. Duke University
    Quark-gluon plasma. Duke University

    CERN researchers recreated the universe’s primordial soup in miniature format by colliding lead atoms with extremely high energy in the 27 km long particle accelerator, the LHC in Geneva. The primordial soup is a so-called quark-gluon plasma and researchers from the Niels Bohr Institute, among others, have measured its liquid properties with great accuracy at the LHC’s top energy. The results were submitted to Physical Review Letters, which is the top scientific journal for nuclear and particle physics.

    “The analyses of the collisions make it possible, for the first time, to measure the precise characteristics of a quark-gluon plasma at the highest energy ever and to determine how it flows,” explains You Zhou, who is a postdoc in the ALICE research group at the Niels Bohr Institute.

    CERN ALICE Icon HUGE
    ALICE Run Control Center
    CERN ALICE New
    CERN ALICE New II
    CERN ALICE and the Control Room

    You Zhou, together with a small, fast-working team of international collaboration partners, led the analysis of the new data and measured how the quark-gluon plasma flows and fluctuates after it is formed by the collisions between lead ions.

    The focus has been on the quark-gluon plasma’s collective properties, which show that this state of matter behaves more like a liquid than a gas, even at the very highest energy densities. The new measurements, which uses new methods to study the correlation between many particles, make it possible to determine the viscosity of this exotic fluid with great precision.

    You Zhou explains that the experimental method is very advanced and is based on the fact that when two spherical atomic nuclei are shot at each other and hit each other a bit off center, a quark-gluon plasma is formed with a slightly elongated shape somewhat like an American football. This means that the pressure difference between the centre of this extremely hot ‘droplet’ and the surface varies along the different axes. The pressure differential drives the expansion and flow and consequently one can measure a characteristic variation in the number of particles produced in the collisions as a function of the angle.

    Jens Jørgen Gaardhøje adds that they are now in the process of mapping this state with ever increasing precision — and even further back in time.

    See the full article here .

    Please help promote STEM in your local schools

    stem

    STEM Education Coalition

     
  • richardmitnick 8:34 am on February 26, 2016 Permalink | Reply
    Tags: , , , , , , Quark-gluon plasma   

    From phys.org: “The universe’s primordial soup flowing at CERN” 

    physdotorg
    phys.org

    February 9, 2016

    Researchers have recreated the universe’s primordial soup in miniature format by colliding lead atoms with extremely high energy in the 27 km long particle accelerator, the LHC at CERN in Geneva.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    The primordial soup is a so-called quark-gluon plasma and researchers from the Niels Bohr Institute, among others, have measured its liquid properties with great accuracy at the LHC’s top energy. The results have been submitted to Physical Review Letters.

    Quark gluon plasma

    A few billionths of a second after the Big Bang, the universe was made up of a kind of extremely hot and dense primordial soup of the most fundamental particles, especially quarks and gluons. This state is called quark-gluon plasma. By colliding lead nuclei at a record-high energy of 5.02 TeV in the world’s most powerful particle accelerator, the 27 km long Large Hadron Collider, LHC at CERN in Geneva, it has been possible to recreate this state in the ALICE experiment’s detector and measure its properties.

    “The analyses of the collisions make it possible, for the first time, to measure the precise characteristics of a quark-gluon plasma at the highest energy ever and to determine how it flows,” explains You Zhou, who is a postdoc in the ALICE research group at the Niels Bohr Institute. You Zhou, together with a small, fast-working team of international collaboration partners, led the analysis of the new data and measured how the quark-gluon plasma flows and fluctuates after it is formed by the collisions between lead ions.

    Advanced methods of measurement

    The focus has been on the quark-gluon plasma’s collective properties, which show that this state of matter behaves more like a liquid than a gas, even at the very highest energy densities. The new measurements, which uses new methods to study the correlation between many particles, make it possible to determine the viscosity of this exotic fluid with great precision.

    You Zhou explains that the experimental method is very advanced and is based on the fact that when two spherical atomic nuclei are shot at each other and hit each other a bit off center, a quark-gluon plasma is formed with a slightly elongated shape somewhat like an American football. This means that the pressure difference between the centre of this extremely hot ‘droplet’ and the surface varies along the different axes. The pressure differential drives the expansion and flow and consequently one can measure a characteristic variation in the number of particles produced in the collisions as a function of the angle.

    Mapping the primordial soup

    “It is remarkable that we are able to carry out such detailed measurements on a drop of ‘early universe’, that only has a radius of about one millionth of a billionth of a meter. The results are fully consistent with the physical laws of hydrodynamics, i.e. the theory of flowing liquids and it shows that the quark-gluon plasma behaves like a fluid. It is however a very special liquid, as it does not consist of molecules like water, but of the fundamental particles quarks and gluons,” explains Jens Jørgen Gaardhøje, professor and head of the ALICE group at the Niels Bohr Institute at the University of Copenhagen.

    Jens Jørgen Gaardhøje adds that they are now in the process of mapping this state with ever increasing precision—and even further back in time.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 4:43 pm on September 10, 2015 Permalink | Reply
    Tags: , , , , Quark-gluon plasma   

    From BNL: “Tiny Drops of Early Universe ‘Perfect’ Fluid” 

    Brookhaven Lab

    August 31, 2015
    Karen McNulty Walsh, (631) 344-8350 or Peter Genzer, (631) 344-3174

    1
    The upper panel of this image, created based on calculations by Brookhaven Lab nuclear theorist Bjoern Schenke, represents initial hot spots created by collisions of one, two, and three-particle ions with heavy nuclei. The lower panel shows the geometrical patterns of particle flow that would be expected if the small-particle collisions are creating tiny hot spots of quark-gluon plasma. No image credit.

    The Relativistic Heavy Ion Collider (RHIC), a particle collider for nuclear physics research at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, smashes large nuclei together at close to the speed of light to recreate the primordial soup of fundamental particles that existed in the very early universe.

    BNL RHIC Campus
    BNL RHIC

    Experiments at RHIC—a DOE Office of Science User Facility that attracts more than 1,000 collaborators from around the world—have shown that this primordial soup, known as quark-gluon plasma (QGP), flows like a nearly friction free “perfect” liquid. New RHIC data just accepted for publication in the journal Physical Review Letters now confirm earlier suspicions that collisions of much smaller particles can also create droplets of this free-flowing primordial soup, albeit on a much smaller scale, when they collide with the large nuclei.

    “These tiny droplets of quark-gluon plasma were at first an intriguing surprise,” said Berndt Mueller, Associate Laboratory Director for Nuclear and Particle Physics at Brookhaven. “Physicists initially thought that only the nuclei of large atoms such as gold would have enough matter and energy to set free the quark and gluon building blocks that make up protons and neutrons. But the flow patterns detected by RHIC’s PHENIX collaboration in collisions of helium-3 nuclei with gold ions now confirm that these smaller particles are creating tiny samples of perfect liquid QGP.”

    These results build on earlier findings from collisions of two-particle ions known as deuterons with gold ions at RHIC, as well as proton-lead and proton-proton collisions at Europe’s Large Hadron Collider (LHC).

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    They also set the stage for the current run colliding protons with gold at RHIC.

    “The idea that collisions of small particles with larger nuclei might create minute droplets of primordial quark-gluon plasma has guided a series of experiments to test this idea and alternative explanations, and stimulated a rich debate about the implications of these findings,” said University of Colorado physicist Jamie Nagle, a co-spokesperson of the PHENIX collaboration at RHIC. “These experiments are revealing the key elements required for creating quark-gluon plasma and could also offer insight into the initial state characteristics of the colliding particles.”

    Geometrical flow patterns

    2
    RHIC’s PHENIX detector

    The discovery of the “perfect” liquid at RHIC, announced definitively in 2005, was largely based on observations of particles flowing in an elliptical pattern from the matter created in RHIC’s most energetic gold-gold collisions. This flow was a clear sign that particles emerging from the collisions were behaving in a correlated, or collective, way that contrasted dramatically with the uniformly expanding gas the scientists had expected. Additional experiments confirmed that this liquid is indeed composed of visible matter’s most fundamental building blocks, quarks and gluons, no longer confined within individual protons and neutrons, and that the flow occurs with minimal resistance—making it a nearly “perfect” liquid QGP.

    “Experiments colliding smaller particles with the heavy ions were originally designed as control experiments because they weren’t supposed to create the QGP,” Nagle said. “But observations at the LHC of very energetic proton-proton collisions and later experiments there colliding protons with lead revealed hints that particles streaming from those tiny collisions were also behaving collectively and flowing. It looked a lot like some of the perfect liquid signatures originally discovered in gold-gold collisions at RHIC, and later in lead-lead collisions at the LHC.”

    When RHIC physicists checked data from the RHIC run of 2008, when deuterons (a nucleus made of one proton and one neutron) were smashed into gold ions, they saw a similar pattern.

    “Since the deuteron is two particles, it creates two separate impacts on the nucleus—two hot spots that appear to merge and form an elongated drop of QGP,” Nagle said.

    Definitive tests

    Those observations triggered the idea of testing for flow patterns in a range of more tightly controlled experiments, which is only possible at RHIC, where physicists can collide a wide variety of ions to control the shape of the droplets of matter created. With additional deuteron-gold collisions already in hand, the RHIC scientists set out to collide three-particle helium-3 nuclei (each made of two protons and one neutron) with gold—and later, single protons with gold.

    “The PHENIX detector can pick up particles coming out of collisions very far forward and backward from the collision point. This large angle coverage allows us to measure the flow in these small collision systems,” said Shengli Huang, a PHENIX collaborator from Vanderbilt University who carried out the analysis. “PHENIX also has a trigger detector that picks up and records the most violent collisions—the ones in which the flow pattern is most apparent,” he said.

    The analysis of those events, as described in the new paper, reveals that the helium-gold collisions exhibit a triangular pattern of flow that the scientists say is consistent with the creation of three tiny droplets of QGP. They also say the data indicate that these small particle collisions could be producing the extreme temperatures required to free quarks and gluons—albeit at a much smaller, more localized scale than in the relatively big domains of QGP created in collisions of two heavy ions.

    “This is a pretty definitive measurement,” Nagle said. “The paper has a plot of elliptical and triangular flow that pretty much matches the hydrodynamic flow calculations we’d expect for QGP. We are really engineering different shapes of the QGP to manipulate it and see how it behaves.”

    There are other key signatures of QGP formation, such as the stopping of energetic particle jets, which have not been detected in the tiny droplets. And other theoretical explanations suggest the flow patterns resulting from some of the small particle-nucleus collisions could emerge from the interactions of gluons within the colliding particles, rather than from the formation of QGP.

    “At this time, the only theoretical framework that reproduces the patterns we’re observing in deuteron-gold and helium-3-gold collisions is fluid dynamics,” said Bjoern Schenke, a nuclear theorist at Brookhaven Lab. “It remains to be seen if alternative models can describe these patterns as well.”

    If other models also turn out to be compatible with the helium-3-gold data, physicists will want to explore whether these models make predictions that differ from those of the hydrodynamic flow model, and for which types of collisions.

    “The good news is that RHIC, with its unrivaled versatility, will likely be able to study any system that can discriminate between different models,” Mueller said.

    Research at RHIC is funded primarily by the DOE Office of Science.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    BNL Campus

    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

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: