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  • richardmitnick 11:36 am on February 1, 2020 Permalink | Reply
    Tags: "Exploring strangeness and the primordial Universe", , , , , , , QGP-quark-gluon plasma”,   

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

    From University of Arizona



    January 31, 2020

    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).


    CERN map

    CERN LHC Maximilien Brice and Julien Marius Ordan

    CERN LHC particles



    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    CERN/ALICE Detector

    CERN CMS New

    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    Secondly, Rafelski follows the narrative with a commented set of his own unpublished work, focusing on pioneering theories and QGP discovery.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].

    BNL RHIC Campus


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    About Science X in 100 words

    Science X™ 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 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
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    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    U Arizona mirror lab-Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

    University of Arizona’s Biosphere 2, located in the Sonoran desert. An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

  • richardmitnick 11:31 am on May 24, 2019 Permalink | Reply
    Tags: "STAR Detector has a New Inner Core", , , 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, QGP-quark-gluon plasma”, 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

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


    BNL/RHIC Star Detector

    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.

    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.


    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.


    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.

    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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    BNL Campus

    BNL Center for Functional Nanomaterials



    BNL RHIC Campus

    BNL/RHIC Star Detector


    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 3:42 pm on February 13, 2019 Permalink | Reply
    Tags: "Building a billion pixel detector for the Large Hadron Collider, , , , , , QGP-quark-gluon plasma”, , STFC’s Daresbury Laboratory   

    From Science and Technology Facilities Council: “Building a billion pixel detector for the Large Hadron Collider” 

    From Science and Technology Facilities Council

    13 February 2019

    Wendy Ellison
    STFC Communications
    Daresbury Laboratory
    Sci-Tech Daresbury
    WA4 4AD
    Tel: 01925 603232

    Scientists, engineers and technicians at Daresbury Laboratory are playing a key role in building ground-breaking new technologies that will enable a major upgrade of the ALICE experiment, one of the four main detectors at the Large Hadron Collider at CERN.

    STFC Daresbury Laboratory-Hub for Pioneering Research

    CERN/ALICE Detector

    Gary Markey and Terry Lee, mechanical technicians at Daresbury Laboratory, building the staves that are now on their way to ALICE at CERN.
    (Credit: STFC)

    University of Liverpool Physicist, Dr Giacomo Contin, prepares the staves for shipment from Daresbury to CERN.
    (Credit: STFC)

    Weighing more than the Eiffel Tower and sitting in a vast cavern 56m below the ground, ALICE acts like a giant microscope that is used to observe and study a state of matter that was last present in the universe just billionths of a second after the Big Bang. The LHC is used to create this matter, which has a temperature around 400,000 times that of the sun, by accelerating and then colliding heavy nuclei of lead. Research at ALICE allows us to reconstruct and provide new insights into the physics of the early universe when, 13.8 billion years ago, in the moments after the Big Bang, the Universe consisted of a primordial soup of particles called Quark-Gluon Plasma.

    Quark-Gluon Plasma from BNL RHIC

    ‘Perfect liquid’ quark-gluon plasma is the most vortical fluid from phys.org

    The ALICE upgrade is a significant international project, and the team at STFC’s Daresbury Laboratory, in collaboration with the University of Liverpool, has been developing and building ground-breaking new technologies as part of a new Inner Tracking System. Extremely thin and highly-pixelated sensors, together with ultra-light support structures will boost the tracking performance of ALICE by a factor of a hundred. It will be the thinnest, most pixelated tracker at the LHC, capable of identifying and measuring the energy of particles created by the LHC’s collisions at lower energies than any of the other LHC experiments.

    The Daresbury-Liverpool team is building 30 staves of this new generation of sensor, each containing millions of pixels. The staves, which frame and support the sensors, are now being carefully transported to CERN in batches every six weeks until the end of September, where they will be tested before being installed, officially making ALICE a billion pixel detector.

    Dr Roy Lemmon, physicist and lead for the ALICE upgrade project at STFC’s Daresbury Laboratory, which is located at Sci-Tech Daresbury, said: “This project highlights the skills and significant role of the UK’s researchers in the development of new generations of technology for, in this case, ALICE, part of the world’s largest science experiment. It’s very exciting to be part of something that will not only help solve our science challenges, but which could also impact our lives in a really positive way, such as through improvements in medical imaging, through the development of new technologies.”

    “The ALICE upgrade is taking place during the scheduled two-year shutdown for the LHC. The newly-upgraded experiment will start taking data in 2021.

    Further information about ALICE at the CERN website.

    Further information about Daresbury Laboratory at the STFC website.

    See the full article here .


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    STFC Hartree Centre

    Helping build a globally competitive, knowledge-based UK economy

    We are a world-leading multi-disciplinary science organisation, and our goal is to deliver economic, societal, scientific and international benefits to the UK and its people – and more broadly to the world. Our strength comes from our distinct but interrelated functions:

    Universities: we support university-based research, innovation and skills development in astronomy, particle physics, nuclear physics, and space science
    Scientific Facilities: we provide access to world-leading, large-scale facilities across a range of physical and life sciences, enabling research, innovation and skills training in these areas
    National Campuses: we work with partners to build National Science and Innovation Campuses based around our National Laboratories to promote academic and industrial collaboration and translation of our research to market through direct interaction with industry
    Inspiring and Involving: we help ensure a future pipeline of skilled and enthusiastic young people by using the excitement of our sciences to encourage wider take-up of STEM subjects in school and future life (science, technology, engineering and mathematics)

    We support an academic community of around 1,700 in particle physics, nuclear physics, and astronomy including space science, who work at more than 50 universities and research institutes in the UK, Europe, Japan and the United States, including a rolling cohort of more than 900 PhD students.

    STFC-funded universities produce physics postgraduates with outstanding high-end scientific, analytic and technical skills who on graduation enjoy almost full employment. Roughly half of our PhD students continue in research, sustaining national capability and creating the bedrock of the UK’s scientific excellence. The remainder – much valued for their numerical, problem solving and project management skills – choose equally important industrial, commercial or government careers.

    Our large-scale scientific facilities in the UK and Europe are used by more than 3,500 users each year, carrying out more than 2,000 experiments and generating around 900 publications. The facilities provide a range of research techniques using neutrons, muons, lasers and x-rays, and high performance computing and complex analysis of large data sets.

    They are used by scientists across a huge variety of science disciplines ranging from the physical and heritage sciences to medicine, biosciences, the environment, energy, and more. These facilities provide a massive productivity boost for UK science, as well as unique capabilities for UK industry.

    Our two Campuses are based around our Rutherford Appleton Laboratory at Harwell in Oxfordshire, and our Daresbury Laboratory in Cheshire – each of which offers a different cluster of technological expertise that underpins and ties together diverse research fields.

    The combination of access to world-class research facilities and scientists, office and laboratory space, business support, and an environment which encourages innovation has proven a compelling combination, attracting start-ups, SMEs and large blue chips such as IBM and Unilever.

    We think our science is awesome – and we know students, teachers and parents think so too. That’s why we run an extensive Public Engagement and science communication programme, ranging from loans to schools of Moon Rocks, funding support for academics to inspire more young people, embedding public engagement in our funded grant programme, and running a series of lectures, travelling exhibitions and visits to our sites across the year.

    Ninety per cent of physics undergraduates say that they were attracted to the course by our sciences, and applications for physics courses are up – despite an overall decline in university enrolment.

  • richardmitnick 1:31 pm on January 30, 2019 Permalink | Reply
    Tags: , , , , Brookhaven STAR collaboration, , , , QGP-quark-gluon plasma”   

    From Lehigh University: “Big Bang Query” 

    From Lehigh University

    Mapping how a mysterious liquid became all matter

    The leading theory about how the universe began is the Big Bang, which says that 14 billion years ago the universe existed as a singularity, a one-dimensional point, with a vast array of fundamental particles contained within it. Extremely high heat and energy caused it to inflate and then expand into the cosmos as we know it?and, the expansion continues to this day.

    The initial result of the Big Bang was an intensely hot and energetic liquid that existed for mere microseconds that was around 10 billion degrees Fahrenheit (5.5 billion Celsius). This liquid contained nothing less than the building blocks of all matter. As the universe cooled, the particles decayed or combined giving rise to…well, everything.

    Quark-gluon plasma (QGP) is the name for this mysterious substance so called because it was made up of quarks — the fundamental particles — and gluons, which physicist Rosi J. Reed describes as “what quarks use to talk to each other.”

    Quark gluon plasma. Duke University

    Scientists like Reed, an assistant professor in Lehigh University’s Department of Physics whose research includes experimental high-energy physics, cannot go back in time to study how the Universe began. So they re-create the circumstances, by colliding heavy ions, such as Gold, at nearly the speed of light, generating an environment that is 100,000 times hotter than the interior of the sun. The collision mimics how quark-gluon plasma became matter after the Big Bang, but in reverse: the heat melts the ions’ protons and neutrons, releasing the quarks and gluons hidden inside them.

    There are currently only two operational accelerators in the world capable of colliding heavy ions — and only one in the U.S.: Brookhaven National Lab’s Relativistic Heavy Ion Collider (RHIC). It is about a three-hour drive from Lehigh, in Long Island, New York.

    BNL RHIC Campus


    Reed is part of the STAR Collaboration , an international group of scientists and engineers running experiments on the Solenoidal Tracker at RHIC (STAR). The STAR detector is massive and is actually made up of many detectors. It is as large as a house and weighs 1,200 tons. STAR’s specialty is tracking the thousands of particles produced by each ion collision at RHIC in search of the signatures of quark-gluon plasma.

    BNL/RHIC Star Detector

    “When running experiments there are two ‘knobs’ we can change: the species — such as gold on gold or proton on proton — and the collision energy,” says Reed. “We can accelerate the ions differently to achieve different energy-to-mass ratio.”

    Using the various STAR detectors, the team collides ions at different collision energies. The goal is to map quark-gluon plasma’s phase diagram, or the different points of transition as the material changes under varying pressure and temperature conditions. Mapping quark-gluon plasma’s phase diagram is also mapping the nuclear strong force, otherwise known as Quantum Chromodynamics (QCD), which is the force that holds positively charged protons together.

    “There are a bunch of protons and neutrons in the center of an ion,” explains Reed. “These are positively charged and should repel, but there’s a ‘strong force’ that keeps them together? strong enough to overcome their tendency to come apart.”

    Understanding quark-gluon plasma’s phase diagram, and the location and existence of the phase transition between the plasma and normal matter is of fundamental importance, says Reed.

    “It’s a unique opportunity to learn how one of the four fundamental forces of nature operates at temperature and energy densities similar to those that existed only microseconds after the Big Bang,” says Reed.

    Upgrading the RHIC detectors to better map the “strong force”

    The STAR team uses a Beam Energy Scan (BES) to do the phase transition mapping. During the first part of the project, known as BES-I, the team collected observable evidence with “intriguing results.” Reed presented these results at the 5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan in Hawaii in October 2018 in a talk titled: “Testing the quark-gluon plasma limits with energy and species scans at RHIC.”

    However, limited statistics, acceptance, and poor event plane resolution did not allow firm conclusions for a discovery. The second phase of the project, known as BES-II, is going forward and includes an improvement that Reed is working on with STAR team members: an upgrade of the Event Plan Detector. Collaborators include scientists at Brookhaven as well as at Ohio State University.

    The STAR team plans to continue to run experiments and collect data in 2019 and 2020, using the new Event Plan Detector. According to Reed, the new detector is designed to precisely locate where the collision happens and will help characterize the collision, specifically how “head on” it is.

    “It will also help improve the measurement capabilities of all the other detectors,” says Reed.

    The STAR collaboration expects to run their next experiments at RHIC in March 2019.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Lehigh University is an American private research university in Bethlehem, Pennsylvania. It was established in 1865 by businessman Asa Packer. Its undergraduate programs have been coeducational since the 1971–72 academic year. As of 2014, the university had 4,904 undergraduate students and 2,165 graduate students. Lehigh is considered one of the twenty-four Hidden Ivies in the Northeastern United States.

    Lehigh has four colleges: the P.C. Rossin College of Engineering and Applied Science, the College of Arts and Sciences, the College of Business and Economics, and the College of Education. The College of Arts and Sciences is the largest, which roughly consists of 40% of the university’s students.The university offers a variety of degrees, including Bachelor of Arts, Bachelor of Science, Master of Arts, Master of Science, Master of Business Administration, Master of Engineering, Master of Education, and Doctor of Philosophy.

    Lehigh has produced Pulitzer Prize winners, Fulbright Fellows, members of the American Academy of Arts & Sciences and of the National Academy of Sciences, and National Medal of Science winners.

  • richardmitnick 12:50 pm on January 4, 2019 Permalink | Reply
    Tags: , Nuclear phase diagram, , , , QGP-quark-gluon plasma”, 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
    (631) 344-8350 or

    Peter Genzer
    (631) 344-3174

    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

    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

    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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    BNL Campus



    BNL RHIC Campus

    BNL/RHIC Star Detector


    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 1:44 pm on October 5, 2018 Permalink | Reply
    Tags: “We have developed new and powerful tools to investigate the properties of the small droplet of QGP (early universe) that we create in the experiments”, , , , , QGP-quark-gluon plasma”, The state of the Early Universe: The beginning was fluid, The transport properties of the Quark-Gluon Plasma will determine the final shape of the cloud of produced particles after the collision so this is our way of approaching the moment of QGP creation it, We want to know what happened in the beginning of the collision and first few moments afterwards, Working with the LHC replacing the lead-ions usually used for collisions with Xenon-ions   

    From Niels Bohr Institute: “The state of the Early Universe: The beginning was fluid” 

    University of Copenhagen

    Niels Bohr Institute bloc

    From Niels Bohr Institute

    04 October 2018

    You Zhou, Postdoc
    Experimental Particle Physics
    Niels Bohr Institute, University of Copenhagen
    Email: you.zhou@nbi.ku.dk
    Phone: +45 35 33 12 82

    Scientists from the Niels Bohr Institute, University of Copenhagen, and their colleagues from the international ALICE collaboration recently collided Xenon nuclei, in order to gain new insights into the properties of the Quark-Gluon Plasma (the QGP) – the matter that the universe consisted of up to a microsecond after the Big Bang.

    The QGP, as the name suggests, is a special state consisting of the fundamental particles, the quarks, and the particles that bind the quarks together, the gluons. The result was obtained using the ALICE experiment at the 27 km long superconducting Large Hadron Collider (LHC) at CERN. The result is now published in Physics Letters B.

    Fig. 1 [Left] An event from the first Xenon-Xenon collision at the Large Hadron Collider at the top energy of the Large Hadron Collider (5.44 TeV ) registered by ALICE [credit: ALICE]. Every colored track (The blue lines) corresponds to the trajectory of a charged particle produced in a single collision; [Right] formation of anisotropic flow in relativistic heavy-ion collisions due to the geometry of the hot and dense overlap zone (shown in red color).

    The beginning was a liquid state of affairs

    The particle physicists at the Niels Bohr Institute have obtained new results, working with the LHC, replacing the lead-ions, usually used for collisions, with Xenon-ions. Xenon is a “smaller” atom with fewer nucleons in its nucleus. When colliding ions, the scientists create a fireball that recreates the initial conditions of the universe at temperatures in excess of several thousand billion degrees. In contrast to the Universe, the lifetime of the droplets of QGP produced in the laboratory is ultra short, a fraction of a second (In technical terms, only about 10-22 seconds). Under these conditions the density of quarks and gluons is very large and a special state of matter is formed in which quarks and gluons are quasi-free (dubbed the strongly interacting QGP). The experiments reveal that the primordial matter, the instant before atoms formed, behaves like a liquid that can be described in terms of hydrodynamics.

    How to approach “the moment of creation”

    “One of the challenges we are facing is that, in heavy ion collisions, only the information of the final state of the many particles which are detected by the experiments are directly available – but we want to know what happened in the beginning of the collision and first few moments afterwards”, You Zhou, Postdoc in the research group Experimental Subatomic Physics at the Niels Bohr Institute, explains. “We have developed new and powerful tools to investigate the properties of the small droplet of QGP (early universe) that we create in the experiments”. They rely on studying the spatial distribution of the many thousands of particles that emerge from the collisions when the quarks and gluons have been trapped into the particles that the Universe consists of today. This reflects not only the initial geometry of the collision, but is sensitive to the properties of the QGP. It can be viewed as a hydrodynamical flow.” The transport properties of the Quark-Gluon Plasma will determine the final shape of the cloud of produced particles, after the collision, so this is our way of approaching the moment of QGP creation itself”, You Zhou says.

    Two main ingredients in the soup: Geometry and viscosity

    The degree of anisotropic particle distribution – the fact that there are more particles in certain directions – reflects three main pieces of information: The first is, as mentioned, the initial geometry of the collision. The second is the conditions prevailing inside the colliding nucleons. The third is the shear viscosity of the Quark-Gluon Plasma itself. Shear viscosity expresses the liquid’s resistance to flow, a key physical property of the matter created. “It is one of the most important parameters to define the properties of the Quark-Gluon Plasma”, You Zhou explains, “ because it tells us how strongly the gluons bind the quarks together “.

    The Xenon experiments yield vital information to challenge theories and models

    “With the new Xenon collisions, we have put very tight constraints on the theoretical models that describe the outcome. No matter the initial conditions, Lead or Xenon, the theory must be able to describe them simultaneously. If certain properties of the viscosity of the quark gluon plasma are claimed, the model has to describe both sets of data at the same time, says You Zhou. The possibilities of gaining more insight into the actual properties of the “primordial soup” are thus enhanced significantly with the new experiments. The team plans to collide other nuclear systems to further constrain the physics, but this will require significant development of new LHC beams.

    Science is not a lonesome affair, far from it

    “This is a collaborative effort within the large international ALICE Collaboration, consisting of more than 1800 researchers from 41 countries and 178 institutes”. You Zhou emphasised.

    See the full article here .


    Stem Education Coalition

    Niels Bohr Institute Campus

    The Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

    The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

    During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

    On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

    The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

    The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

  • richardmitnick 1:08 pm on December 15, 2017 Permalink | Reply
    Tags: , , , , , , , Plotting the Phase Transitions, QGP-quark-gluon plasma”, Recreating the Beginning of the Universe   

    From BNL: “How to Map the Phases of the Hottest Substance in the Universe” 

    Brookhaven Lab

    December 11, 2017
    Shannon Brescher Shea

    Scientists are searching for the critical point of quark-gluon plasma, the substance that formed just after the Big Bang. Finding where quark-gluon plasma abruptly changes into ordinary matter can reveal new insights.

    BNL RHIC Campus

    BNL/RHIC Star Detector


    The universe began as a fireball 250,000 times hotter than the core of the sun. Just microseconds after the Big Bang, the protons and neutrons that make up the building blocks of nuclei, the heart of atoms, hadn’t yet formed. Instead, we had the quark-gluon plasma, a blazing 4 trillion degree Celsius liquid of quarks, gluons, and other particles such as electrons. At that very earliest moment, it was as if the entire universe was a tremendous, churning lake of gluon “water” filled with quark “pebbles.”

    In less than a heartbeat, the universe cooled, “freezing” the lake. Instead of becoming a solid block, everything separated out into clusters of quark “pebbles” connected by gluon “ice.” When some of these quarks joined together, they became our familiar protons and neutrons. After a few minutes, those protons and neutrons came together to form nuclei, which make up the cores of atoms. Quarks and gluons are two of the most basic subatomic particles in existence. Today, quarks make up protons and neutrons while gluons hold the quarks together.

    But since the Big Bang, quarks and gluons have never appeared by themselves in ordinary matter. They’re always found within protons or neutrons.

    Except for a few very special places in the world. In facilities supported by the Department of Energy’s (DOE) Office of Science, scientists are crashing gold ions into each other to recreate quark-gluon plasma. They’re working to map how and when quark-gluon plasma transforms into ordinary matter. Specifically, they’re looking for the critical point – that strange and precise place that marks a change from one type of transition to another between quark-gluon plasma and our familiar protons and neutrons.

    Recreating the Beginning of the Universe

    Because quark-gluon plasma could provide insight into universe’s origins, scientists have wanted to understand it for decades. It could help scientists better comprehend how today’s complex matter arises from the relatively straightforward laws of physics.

    But scientists weren’t able to study quark-gluon plasma experimentally at high energies until 2000. That’s when researchers at DOE’s Brookhaven National Laboratory flipped the switch on the Relativistic Heavy Ion Collider (RHIC), an Office of Science user facility. This particle accelerator was the first to collide beams of heavy ions (heavy atoms with their electrons stripped off) head-on into each other.

    It all starts with colliding ions made of protons and neutrons into each other. The bunches of ions smash together and create about a hundred thousand collisions a second. When the nuclei of the ions first collide, quarks and gluons break off and scatter. RHIC’s detectors identify and analyze these particles to help scientists understand what is happening inside the collisions.

    As the collision reaches temperatures hot enough to melt protons and neutrons, the quark-gluon plasma forms and then expands. When the collisions between nuclei aren’t perfectly head-on, the plasma flows in an elliptical pattern with almost zero resistance. It actually moves 10 billion trillion times fasterExternal link than the most powerful tornado. The quarks in it strongly interact, with many particles constantly bouncing off their many neighbors and passing gluons back and forth. If the universe began in a roiling quark-gluon lake, inside the RHIC is a miniscule but ferocious puddle.

    Then, everything cools down. The quarks and gluons cluster into protons, neutrons, and other subatomic particles, no longer free.

    All of this happens in a billionth of a trillionth of a second.

    After running these experiments for years, scientists at RHIC finally found what they were looking for. The data from billions of collisions gave them enough evidence to declare that they had created quark-gluon plasma. Through temperature measurements, they could definitively say the collisions created by RHIC were hot enough to melt protons and neutrons, breaking apart the quark-gluon clusters into something resembling the plasma at the very start of the universe.

    Since then, scientists at the Large Hadron Collider at CERN in Geneva have also produced quark-gluon plasma.


    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    Researchers at both facilities are working to better understand this strange form of matter and its phases.

    Plotting the Phase Transitions.

    This diagram plots out what scientists theorize about quark-gluon plasma’s phases using the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Baryon density is the density of the particles in the matter.

    All matter has different phases. A phase is a form where matter has consistent physical properties, such as density, magnetism, and electrical conductivity. The best-known phases are solid, liquid, and gas. For example, water’s conventional phases are ice, liquid water, and steam. Beyond the phases familiar to us, there’s also the plasma phase that makes up stars and the utterly unique quark-gluon plasma.

    Phase transitions, where materials move between phases, reveal a great deal about how matter functions. Materials usually change phases because they experience a change in temperature or pressure.

    “Phase transitions are an amazing phenomenon in nature,” said Jamie Nagle, a professor at the University of Colorado at Boulder who conducts research at RHIC. “Something that molecularly is the same can look and behave in a dramatically different way.”

    Like many types of matter, quark-gluon plasma goes through phase transitions. But because quarks and gluons haven’t existed freely in ordinary matter since the dawn of time, it acts differently than what we’re used to.

    In most circumstances, matter goes through first-order phase transitions. These changes result in major shifts in density, such as from liquid water to ice. These transitions also use or release a lot of heat. Water freezing into ice releases energy; ice melting into water absorbs energy.

    But quark-gluon plasma is different. In quark-gluon plasma, scientists haven’t seen the first-order phase transition. They’ve only seen what they call smooth or continuous cross-over transformations. In this state, gluons move back and forth smoothly between being free and trapped in protons and neutrons. Their properties are changing so often that it’s difficult to distinguish between the plasma and the cloud of ordinary matter. This phase can also happen in ordinary matter, but usually under extreme circumstances. For example, if you boil water at 217 times the pressure of our atmosphere, it’s nearly impossible to tell the difference between the steam and liquid.

    Even though scientists haven’t seen the first-order phase transition yet, the physics theory that describes quark-gluon plasma predicts there should be one. The theory also predicts a particular critical point, where the first-order phase transition ends.

    “This is really the landmark that we’re looking for,” said Krishna Rajagopal, a theoretical physicist and professor at the Massachusetts Institute of Technology (MIT).

    Understanding the relationships between these phases could provide insight into phenomena beyond quark-gluon plasma. In fact, scientists have applied what they’ve learned from studying quark-gluon plasma to better understand superconductors. Scientists can also use this knowledge to understand other places where plasma may occur in the universe, such as stars.

    As John Harris, a Yale University professor, said, “How do stars, for example, evolve? Are there such stars out there that have quark-gluon cores? Could neutron-star mergers go through an evolution that includes quark-gluon plasma in their final moments before they form black holes?”

    The Search Continues

    These collisions have allowed scientists to sketch out the basics of quark-gluon plasma’s phases. So far, they’ve seen that ordinary matter occurs at the temperatures and densities that we find in most of the universe. In contrast, quark-gluon plasma occurs at extraordinarily high temperatures and densities. While scientists haven’t been able to produce the right conditions, theory predicts that quark-gluon plasma or an even more exotic form of matter may occur at low temperatures with very high densities. These conditions could occur in neutron stars, which weigh 10 billion tons per cubic inch.

    Delving deeper into these phases will require physicists to draw from both theory and experimental data.

    Theoretical physics predicts the critical point exists somewhere under conditions that are at lower temperatures and higher densities than RHIC can currently reach. But scientists can’t use theory alone to predict the exact temperature and density where it would occur.

    “Different calculations that do things a bit differently give different predictions,” said Barbara Jacak, the director of the Nuclear Science division at DOE’s Lawrence Berkeley National Laboratory. “So I say, ‘Aha, experiment to the rescue!'”

    What theory can do is provide hints as to what to look for in experiments. Some collisions near the critical point should produce first-order transitions, while others produce smooth cross-over ones. Because each type of phase transition produces different types and numbers of particles, the collisions should, too. As a result, scientists should see large variations in the numbers and types of particles created from collision to collision near the critical point. There may also be big fluctuations in electric charge and other types of phenomena.

    The only way to see these transitions is to collide particles at a wide range of energies. RHIC is the only machine in the world that can do this. While the Large Hadron Collider can produce quark-gluon plasma, it can’t collide heavy ions at low enough energy levels to find the critical point.

    So far, scientists have done an initial “energy scan” where they have run RHIC at a number of different energy levels. However, RHIC’s current capabilities limit the data they’ve been able to collect.

    “We had some very intriguing results, but nothing that was so statistically significant that you could declare victory,” said Rosi Reed, a Lehigh University assistant professor who conducts research at RHIC.

    RHIC is undergoing upgrades to its detector that will vastly increase the number of collisions scientists can study. It will also improve how accurately they can study them. When RHIC relaunches, scientists envision these hints turning into more definitive answers.

    From milliseconds after the Big Bang until now, the blazing lake of quark-gluon plasma has only existed for the smallest fraction of time. But it’s had an outsized influence on everything we see.

    As Gene Van Buren, a scientist at DOE’s Brookhaven National Laboratory, said, “We’re making stuff in the laboratory that no one else has really had the chance to do in human history.”

    See the full article here .

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    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.

  • richardmitnick 4:20 pm on October 27, 2017 Permalink | Reply
    Tags: , , , , , , , QGP-quark-gluon plasma”   

    From ALICE at CERN: “Probing the QGP with heavy flavours: recent results” 

    CERN New Masthead

    16 October 2017
    Elena Bruna

    Heavy quarks, like charm and beauty, are unique probes of the Quark-Gluon Plasma (QGP) created in Pb-Pb collisions at LHC energies. Their production occurs via high-Q2 processes, and therefore it is possible to test pQCD calculations for charm and beauty production at LHC energies. In addition, their large masses imply a short formation time, and therefore a longer exposure to the full system evolution. Measurements of D mesons, as well as electrons and muons from heavy-flavour hadron decays from ALICE during LHC Run 1 have proved strong quenching and collectivity of charm quarks in the QGP.

    There are still some open key questions towards a more quantitative understanding of the processes behind energy loss and collective effects, in particular: are heavy quarks affected by initial state effects? What is the role of recombination of charm quarks with lighter quarks in the hadronization process? Are heavy quarks affected by the collective expansion of the medium, and how is this related to the bulk expansion? The recent ALICE results from LHC Run 2 on both p-Pb and Pb-Pb collisions improve the precision of Run 1 results, opening new avenues to characterize the QGP and initial state effects.

    The p-Pb collisions at √sNN = 5.02 TeV recorded by ALICE in 2016 allowed studies of the nuclear modification factor of D mesons with high precision selecting the events on the basis of their centrality. To avoid the uncertainty on the pp reference, we performed the ratio (QCP) of the D0 pT distributions in central over peripheral p-Pb collisions, considering the different number of binary collisions. The D0 QCP, reported in Fig. 1, shows an enhancement from 1 in the pT range 3-8 GeV/c with a 1.7 level (considering statistical and systematic uncertainty including the one on normalization). The current precision of the measurement is still preventing us from drawing conclusions on the role of the different Cold Nuclear Matter effects and on possible presence of additional hot-medium effects, however it poses an interesting question on what are the mechanisms at play in small systems, and to what extent heavy quarks are influenced by them

    Figure 1: D0 central (0-10%)-to-peripheral (60-100%) nuclear modification factor (QCP) as a function of pT in p-Pb collisions at √sNN = 5.02 TeV (ALICE-PUBLIC-2017-008).

    Moving to heavy-ion collisions, ALICE has measured the nuclear modification factor RAA in Pb-Pb at √sNN = 5.02 TeV. Figure 2 shows the RAA for the average of D0, D+, D*+ mesons as a function of pT, together with that of Ds+ for the 0-10% centrality class.

    The larger statistics from Run 2 data allows for more precise measurements and higher pT reach. The central RAA values are higher for Ds+ mesons w.r.t. non-strange D mesons, but the two measurements are compatible within uncertainties. It is interesting to notice that the TAMU (Phys. Lett. B735 (2014) 445) and PHSD (PRC 93 (2016) 034906) models, which include recombination of charm quarks with the enhanced strange quarks in the QGP, predict a large increase of the Ds+ RAA.

    Figure 2: Average of of D0, D+, D*+ (black) and Ds+ (orange) RAA as a function of pT for 0-10% Pb-Pb collisions at √sNN = 5.02 TeV (ALICE-PUBLIC-2017-003).

    Figure 3: D0, D+ average v2 in 30–50% Pb–Pb collisions at √sNN = 5.02 TeV for events with largest q2 (blue), smallest q2 (red) and using the full sample (grey).

    The observable used to characterize the azimuthal anisotropy of the produced particles is the elliptic flow v2, which quantifies, at low pT, the degree of collectivity of the system. The recent ALICE paper on the D-meson v2 in 30-50% Pb-Pb collisions at √sNN = 5.02 TeV (arXiv:1707.01005) shows a positive v2 at low-intermediate pT, suggesting that charm quarks interact with the medium constituents and are sensitive to the collective expansion of the medium. A step forward in this direction is to measure the D-meson v2 in events with different eccentricity, defined by the second-harmonic flow vector q2, obtained from the azimuthal angles of all the tracks in the event. The average of D0 and D+ v2 was measured for the 60% of events with the smallest q2 and for 20% of the events with the largest q2. The result, shown in Fig.3, shows a significant separation between D-meson v2 in events with large and small q2, suggesting that charm quarks are influenced by the light-hadron bulk collectivity and by event-by-event initial fluctuations. These event engineering techniques are becoming a new testing ground for models to understand the relation between heavy and light quark collectivity.

    The LHC Run 2 has so far provided ALICE with large data samples in different collision systems to start setting constraints on models for heavy-flavour production, energy loss and collectivity. The remaining part of Run 2, together with Run 3 and Run 4, will allow for further improvements of the measurements and new differential observables to pose crucial constraints to theory models.

    See the full article here .

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  • richardmitnick 11:27 am on September 22, 2017 Permalink | Reply
    Tags: 2016 deuteron-gold collisions, , , , , , QGP-quark-gluon plasma”   

    From BNL: “New Evidence for Small, Short-Lived Drops of Early Universe Quark-Gluon Plasma?” 

    Brookhaven Lab

    September 18, 2017
    Karen McNulty Walsh
    (631) 344-8350
    Peter Genzer
    (631) 344-3174

    The PHENIX detector at the Relativistic Heavy Ion Collider (RHIC) with a superimposed image of reconstructed particle tracks picked up by the detector.

    BNL RHIC Campus

    BNL/RHIC Star Detector


    Particles emerging from even the lowest energy collisions of small deuterons with large heavy nuclei at the Relativistic Heavy Ion Collider (RHIC)—a U.S. Department of Energy Office of Science User Facility for nuclear physics research at DOE’s Brookhaven National Laboratory—exhibit behavior scientists associate with the formation of a soup of quarks and gluons, the fundamental building blocks of nearly all visible matter. These results from RHIC’s PHENIX experiment suggest that these small-scale collisions might be producing tiny, short-lived specks of matter that mimics what the early universe was like nearly 14 billion years ago, just after the Big Bang.

    Scientists built RHIC, in large part, to create this “quark-gluon plasma” (QGP) so they could study its properties and learn how Nature’s strongest force brings quarks and gluons together to form the protons, neutrons, and atoms that make up the visible universe today. But they initially expected to see signs of QGP only in highly energetic collisions of two heavy ions such as gold. The new findings—correlations in the way particles emerge from the collisions that are consistent with what physicists have observed in the more energetic large-ion collisions—add to a growing body of evidence from RHIC and Europe’s Large Hadron Collider (LHC) that QGP may be created in smaller systems as well.

    The PHENIX collaboration has submitted the findings in two separate papers to the journals Physical Review Letters and Physical Review C, and will present these results at a meeting in Krakow, Poland this week.

    “These are the first papers that come out of the 2016 deuteron-gold collisions, and this is one indication that we are probably creating QGP in small systems,” said Julia Velkovska, a deputy spokesperson for PHENIX from Vanderbilt University. “But there are other things that we have seen in the larger systems that we have yet to investigate in this new data. We’ll be looking for other evidence of QGP in the small systems using different ways to study the properties of the system we are creating,” she said.

    Collective flow

    One of the earliest signs that RHIC’s collisions of two gold ions were creating QGP came in the form of “collective flow” of particles. More particles emerged from the “equator” of two semi-overlapping colliding ions than perpendicular to the collision direction. This elliptical flow pattern, scientists believe, is caused by interactions of the particles with the nearly “perfect”—meaning free-flowing—liquid-like QGP created in the collisions. Since then, collisions of smaller particles with heavy ions have resulted in similar flow patterns at both RHIC and the LHC, albeit on a smaller scale. There has also been evidence that flow patterns have a strong relationship with the geometrical shape of the projectile particle that is colliding with the larger nucleus.

    “With these results in hand, we wanted to try smaller and smaller systems at different energies,” Velkovska said. “If you change the energy, you can change the time that the system stays in the liquid phase, and maybe make it disappear.”

    In other words, they wanted to see if they could turn the creation of QGP off.

    “After so many years we have learned that when QGP is created in the collisions we know how to recognize it, but that doesn’t mean we really understand how it works,” Velkovska said. “We are trying to understand how the perfect-fluid behavior emerges and evolves. What we are doing now—going down in energy, changing the size—is an effort to learn how this behavior arises in different conditions. RHIC is the only collider in the world that allows such a range of studies over different collision energies with different colliding particle species.”

    Turning down the energy

    Over a period of about five weeks in 2016, the PHENIX team explored collisions of deuterons (made of one proton and one neutron) with gold ions at four different energies (200, 62.4, 39, and 19.6 billion electron volts, or GeV).

    “Thanks to the versatility of RHIC and the ability of the staff in Brookhaven’s Collider-Accelerator Department to quickly switch and tune the machine for different collision energies, PHENIX was able to record more than 1.5 billion collisions in this short period of time,” Velkovska said.

    For each collision energy in the beam energy scan, the central panel shows an early-time snapshot of the coordinates of quarks emerging from a deuteron-gold (d-Au) collision as simulated in a transport-model theory calculation. The right panel shows the elliptic flow of the final-state hadrons as measured by PHENIX (closed points), along with the prediction from the theory (solid curve). No image credit.

    For the paper submitted to PRC, Darren McGlinchey, a PHENIX collaborator from Los Alamos National Laboratory, led an analysis of how particles emerged along the elliptical plane of the collisions as a function of their momentum, how central (fully overlapping) the collisions were, and how many particles were produced.

    “Using a deuteron projectile produces a highly elliptical shape, and we observed a persistence of that initial geometry in the particles we detect, even at low energy,” McGlinchey said. Such shape persistence could be caused by interaction with a QGP created in these collisions. “This result is not sufficient evidence to declare that QGP exists, but it is a piece of mounting evidence for it,” he said.

    Ron Belmont, a PHENIX collaborator from the University of Colorado, led an analysis of how the flow patterns of multiple particles (two and four particles at each energy and six at the highest energy) were correlated. Those results were submitted to PRL.

    “We found a very similar pattern in both two- and four-particle correlations for all the different energies, and in six-particle correlations at the highest energy as well,” Belmont said.

    “Both results are consistent that particle flow is observed down to lowest energy. So the two papers work together to paint a nice picture,” he added.

    There are other possible explanations for the findings, including the postulated existence of another form of matter known as color glass condensate that is thought to be dominated by the presence of gluons within the heart of all visible matter.

    “To distinguish color glass condensate from QGP, we need more detailed theoretical descriptions of what these things look like,” Belmont said.

    Velkovska noted that many new students have been recruited to continue the analysis of existing data from the PHENIX experiment, which stopped taking data after the 2016 run to make way for a revamped detector known as sPHENIX.

    “There is a lot more to come from PHENIX,” she said.

    See the full article here .

    Please help promote STEM in your local schools.

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    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.

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