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  • richardmitnick 4:33 pm on August 25, 2014 Permalink | Reply
    Tags: , , , , Quark-gluon plasma,   

    From Livermore Lab: “Calculating conditions at the birth of the universe” 


    Lawrence Livermore National Laboratory

    08/25/2014
    Anne M Stark, LLNL, (925) 422-9799, stark8@llnl.gov

    Using a calculation originally proposed seven years ago to be performed on a petaflop computer, Lawrence Livermore researchers computed conditions that simulate the birth of the universe.

    When the universe was less than one microsecond old and more than one trillion degrees, it transformed from a plasma of quarks and gluons into bound states of quarks – also known as protons and neutrons, the fundamental building blocks of ordinary matter that make up most of the visible universe.

    The theory of quantum chromodynamics (QCD) governs the interactions of the strong nuclear force and predicts it should happen when such conditions occur.

    In a paper appearing in the Aug. 18 edition of Physical Review Letters, Lawrence Livermore scientists Chris Schroeder, Ron Soltz and Pavlos Vranas calculated the properties of the QCD phase transition using LLNL’s Vulcan, a five-petaflop machine. This work was done within the LLNL-led HotQCD Collaboration, involving Los Alamos National Laboratory, Institute for Nuclear Theory, Columbia University, Central China Normal University, Brookhaven National Laboratory and Universität Bielefed in Germany.

    vulcan
    A five Petaflop IBM Blue Gene/Q supercomputer named Vulcan

    This is the first time that this calculation has been performed in a way that preserves a certain fundamental symmetry of the QCD, in which the right and left-handed quarks (scientists call this chirality) can be interchanged without altering the equations. These important symmetries are easy to describe, but they are computationally very challenging to implement.

    “But with the invention of petaflop computing, we were able to calculate the properties with a theory proposed years ago when petaflop-scale computers weren’t even around yet,” Soltz said.

    The research has implications for our understanding of the evolution of the universe during the first microsecond after the Big Bang, when the universe expanded and cooled to a temperature below 10 trillion degrees.

    Below this temperature, quarks and gluons are confined, existing only in hadronic bound states such as the familiar proton and neutron. Above this temperature, these bound states cease to exist and quarks and gluons instead form plasma, which is strongly coupled near the transition and coupled more and more weakly as the temperature increases.

    “The result provides an important validation of our understanding of the strong interaction at high temperatures, and aids us in our interpretation of data collected at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN.” Soltz said.

    Brookhaven RHIC
    RHIC at Brookhaven

    CERN LHC Grand Tunnel
    LHC at CERN

    Soltz and Pavlos Vranas, along with former colleague Thomas Luu, wrote an essay predicting that if there were powerful enough computers, the QCD phase transition could be calculated. The essay was published in Computing in Science & Engineering in 2007, “back when a petaflop really did seem like a lot of computing,” Soltz said. “With the invention of petaflop computers, the calculation took us several months to complete, but the 2007 estimate turned out to be pretty close.”

    The extremely computationally intensive calculation was made possible through a Grand Challenge allocation of time on the Vulcan Blue Gene/Q Supercomputer at Lawrence Livermore National Laboratory.

    See the full article here.

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  • richardmitnick 2:33 pm on December 6, 2013 Permalink | Reply
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    From Brookhaven Lab: “Tiny Drops of Hot Quark Soup—How Small Can They Be?” 

    Brookhaven Lab

    New analyses of deuteron-gold collisions at RHIC reveal that even small particles can create big surprises

    December 6, 2013
    Karen McNulty Walsh

    Scientists designed and built the Relativistic Heavy Ion Collider (RHIC) at the U.S. Department of Energy’s Brookhaven National Laboratory to create and study a form of matter that last existed a fraction of a second after the Big Bang, some 13.8 billion years ago. The early-universe matter is created when two beams of gold nuclei traveling close to the speed of light slam into one another. The high-speed particle smashups pack so much energy into such a tiny space that the hundreds of protons and neutrons making up the nuclei “melt” and release their constituent particles—quarks and gluons—so scientists can study these building blocks of matter as they existed at the dawn of time.

    phenix
    Components of the PHENIX detector at Brookhaven’s Relativistic Heavy Ion Collider (RHIC). PHENIX weighs 4,000 tons. It has large steel magnets and a dozen detector sub-systems that bend and track a wide range of particles while measuring their properties (e.g., momentum and energy) as they emerge from collisions. No image credit.

    Collisions between gold nuclei and deuterons—much smaller particles made of just one proton and one neutron—weren’t supposed to create this superhot subatomic soup known as quark-gluon plasma (QGP). They were designed as a control experiment, to generate data to compare against RHIC’s gold-gold smashups. But new analyses indicate that these smaller particle impacts may be serving up miniscule drops of hot QGP—a finding consistent with similar results from Europe’s Large Hadron Collider (LHC), which can also collide heavy nuclei.

    “Considering that the quark-gluon plasma we create in gold-gold collisions at RHIC fills a space that is approximately the size of the nucleus of a single gold atom, the possible hot spots we’re talking about in these deuteron-gold collisions are much, much smaller—and an intriguing surprise,” said Dave Morrison, a physicist at Brookhaven and co-spokesperson for RHIC’s PHENIX collaboration. The collaboration describes their results in two papers just published by Physical Review Letters, one of which is highlighted by the journal.

    The findings at RHIC and the LHC have triggered active debate about their interpretation. Said PHENIX co-spokesperson Jamie Nagle of the University of Colorado, “There isn’t yet universal agreement about what we’re seeing in these small systems, but if indeed nearly perfect fluid droplets of quark-gluon plasma are being formed, this may be a perfect testing ground for understanding the essential conditions for creating this remarkable state of matter.”

    See the full article here.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 2:04 pm on March 21, 2013 Permalink | Reply
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    From ALICE at CERN: “ALICE 20th Anniversary” 

    CERN New Masthead

    THERE IS A TON OF UNEXPLAINED JARGON IN THIS ARTICLE. IT IS REALLY WRITTEN EXPECTING SPECIALISTS TO BE THE READERS. BUT I OFFER IT FOR ANYONE WHO MIGHT KNOW WHAT IS GOING ON OR WHO MIGHT WISH A STARTING POINT TO DIG IN AND FIND OUT.

    21 March 2013
    Panos Charitos

    20 years ago ALICE started its amazing adventure in the wonderland of strong interactions and the study of extraordinary forms of matter like the Quark Gluon Plasma.

    CERN’s ion programme has a long history and was initiated in 1986 with the acceleration of oxygen ions at 60 and 200 GeV/nucleon, and continued with sulphur ions at 200 GeV/nucleon up to 1993. The first Lead-ion beams at 160 GeV/nucleon became available in 1994. The accelerating chain for 16O and 32S consisted of an ion source of the electron–cyclotron resonance (ECR) type, a radio-frequency quadrupole (RFQ) pre-accelerator, the linear accelerator injector (LINAC I), the PSBooster , the PSand the SPS. For the acceleration of lead ions, a new ECR source, a new RFQ and a new LINAC had to be constructed. The results of the light-ion programme strongly supported its continuation with heavier-ion beams. In particular, the energy densities reached during the collisions appeared to be high enough to be interesting, and many of the suggested signatures for the onset of a quark–gluon plasma phase turned out to be experimentally accessible. The experience gained was instrumental in assessing the feasibility of experiments with lead ions and for indicating the necessary detector modifications. Seven experiments participated in the lead-age adventure.

    Following the previous successes of the heavy-ion physics programme at CERN the idea of a heavy-ion dedicated experiment that would study lead-lead collisions at the new energy scale of the LHC was discussed. During the previous years, the experience gained was instrumental in assessing the feasibility of experiments with lead ions and for indicating the necessary detector modifications that were needed to move with the lead-age adventure at the new scale of the LHC.

    The first appearance of ALICE was in the Evian meeting back in 1992. Jurgen Schukraft recalls that: “We had to do enormous extrapolations because the LHC was a factor of 300 higher in centre-of-mass energy and a factor of 7 in beam mass compared with the light-ion programme, which started in 1986 at both the CERN SPS and the Brookhaven AGS.” A Letter of Intent for a new experiment at the LHC was submitted on 1 March 1993 to the LHC Committee that was formed shortly after the Evian meeting. It marks the first official use of the name ALICE and it was signed by 230 people coming from 42 institutes around the world. It was clearly describing the proposal of the ALICE Collaboration for building a dedicated heavy-ion detector to exploit the unique physics potential of nucleus-nucleus interaction at LHC energies and where the formation of a new phase of matter, the quark gluon plasma is expected. The submission of the letter of intent was followed by a detailed technical proposal that was submitted two years later in 1995 and shortly endorsed by the LHCC and the CERN management.

    early

    mega

    ALICE studies strong interactions by using particles – created inside the hot volume of the Quark Gluon Plasma as it expands and cools down – that live long enough to reach the sensitive detector layers located around the interaction region. The physics programme at ALICE relies on being able to identify all of them – i.e. to determine if they are electrons, photons, pions, etc – and to determine their charge. This involves making the most of the different ways that particles interact with matter. Over twenty years, ALICE has developed a wide range of R&D activities, confronted many challenges in designing and building new detectors that could cope with the physical challenges at the new energy scales. One should also refer to the big data challenge as heavy-ion collisions produce petabytes of data that need to be stored and later analysed in order to get new physics results.

    event

    Following the first run, ALICE successfully reported on the formation of QGP and offered a new insight on the nature of strong interacting matter at extreme densities. The existence of such a phase and its properties are a key issue in QCD for the understanding of confinement and of chiral-symmetry restoration. Wherever you look, from the energy loss of fast quarks to quarkonia, from the details of the dynamical evolution of the system to the very first study of charmed hadrons and the loss of energy, the interplay between , to name just a few, the ALICE results stand out for their quality and relevance. Following the recent proton-lead run that opens new horizons for the heavy-ion community at CERN, ALICE is now looking forward to a series of upgrades during the LS1.

    Paolo Giubellino notes: ‘This has been the result of many years of work and dedication of all of us, and we can all be proud of now sharing this remarkable harvest. It has been an enormous effort, but we can now say it was really worth it, and all share the happiness for this wealth of results. We all contributed to this accomplishment, and we should all draw from it even more motivation to go forward for the next many years to come!'”

    See the full article here.

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  • richardmitnick 6:21 pm on January 18, 2013 Permalink | Reply
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    From Fermilab: “Physics in a Nutshell – The atom splashers” 


    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Friday, Jan. 18, 2013
    Jim Pivarski

    In most particle physics experiments, physicists attempt to concentrate as much energy as possible into a point of space. This allows the formation of new, exotic particles like Higgs bosons that reveal the basic workings of the universe. Other collider experiments have a different goal: to spread the energy among enough particles to make a continuous medium, a droplet of fluid millions of times hotter than the center of the sun. The latter studies, often referred to as heavy-ion physics, require collisions of large nuclei, such as gold or lead, to produce amorphous splashes instead of point-like collisions.

    qgp
    Quark-gluon Plasma at Brookhaven’s RHIC (image NSCL)

    This short-lived state of quark matter is unlike any other known to science. All other liquids, gases, gels and plasmas are governed by forces that weaken with distance… In contrast, the quarks and gluons loosed by a heavy-ion collision are attracted to one another by the nuclear strong force, which does not weaken with distance. As two quarks start to separate from each other, new pairs of quarks and antiquarks join the mix with an attraction of their own.

    Quark matter is the stuff the big bang was made of. In the first microseconds of the universe, all matter was a freely flowing quark-gluon soup [*], which later evaporated into the protons and neutrons that we know today. Yet it is far from understood.

    Heavy-ion collisions in the LHC and RHIC at Brookhaven will tell us more about the origin of our universe.

    Brookhaven RHIC
    Relativistic Heavy Ion Collier (RHIC) at Brookhaven

    CERN CMS New
    CMS – the home of QGP research at CERN’s LHC
    See the full article here.

    *Often described as “quark-gluon plasma” (QGP)

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.


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  • richardmitnick 1:01 pm on November 29, 2012 Permalink | Reply
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    From ALICE at CERN via Quantum Diaries: “The coolest and hottest fluid” 


    Pauline Gagnon

    “The ALICE experiment is dedicated to the study of the quark-gluon plasma. Each year, the LHC operates for a few weeks with lead ions instead of protons. ALICE collects data both during proton-proton collisions and heavy ions collisions. Even when only protons collide, the projectiles are not solid balls like on a billiard table but composite objects. By comparing what can is obtained from heavy ion collisions with proton collisions, the ALICE physicists must first disentangle what comes from having protons in a bound state inside the nucleus as opposed to “free protons”.

    qgp

    So far, it appears that the quark-gluon plasma only formed during heavy-ion collisions since they provide the necessary energy density over a substantial volume (namely, the size of a nucleus). Some of the effects observed, such as the number of particles coming out of the collisions at different angles or momenta, depend in part on the final state created. When the plasma is formed, it reabsorbs many of the particles created, such that fewer particles emerged from the collision.

    By colliding protons and heavy ions, scientists hope to discern what comes from the initial state of the projectile (bound or free protons) and what is caused by the final state (like the suppression of particles emitted when a quark-gluon plasma forms).

    ppg
    A “snapshot” of the debris coming out of a proton-lead ion collision captured by the ALICE detector showing a large number of various particles created from the energy released by the collision.

    The ultimate goal is to study the so-called ‘structure function’, which describes how quarks and gluons are distributed inside protons, when they are free or embedded inside the nucleus.

    More will be studied during the two-month running period with protons colliding on heavy ions planned for the beginning of 2013.”

    See the full article here.

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