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Exploring the matter that filled the early universe by Staff Writers Chicago IL (SPX) Feb 07, 2017
Theorists and scientists conducting experiments that recreate matter as it existed in the very early universe are gathered in Chicago this week to present and discuss their latest results. These experiments, conducted at the world's premier particle colliders - the Relativistic Heavy Ion Collider (RHIC) at the U.S. Department of Energy's Brookhaven National Laboratory, and the Large Hadron Collider (LHC) at the European Center for Nuclear Research (CERN) - are revealing intriguing information about the building blocks of visible matter and the force that holds them together in the universe today. The Quark Matter 2017 conference (QM17) will feature new results describing the particles created as atomic nuclei smash into one another at nearly the speed of light at RHIC and the LHC. These "ultrarelativistic heavy-ion collisions" melt ordinary protons and neutrons, momentarily setting free their inner constituents - quarks and gluons - so scientists can study their behavior and interactions. The physicists want to sort out the detailed properties of the hot "quark-gluon plasma" (QGP), and understand what happens as this primordial soup cools and coalesces to form the more familiar matter of today's world. The two scientific collaborations conducting nuclear physics research at RHIC-STAR and PHENIX, named for their house-sized detectors-will present findings that build on earlier discoveries at this DOE Office of Science User Facility. The two collaborations perform cross-checking analyses to verify results, while also exploiting each detector's unique capabilities and strengths for independent explorations. The QM17 presentations will showcase precision measurements made possible by recent detector upgrades. "These results illustrate how a global community of dedicated scientists is taking full advantage of RHIC's remarkable versatility to explore in depth the structure of nuclear matter over a wide range of temperatures and densities to better understand the dynamic behavior of quarks and gluons and the strong nuclear force," said Berndt Mueller, Associate Laboratory Director for Nuclear and Particle Physics at Brookhaven Lab. "The latest RHIC findings indicate that RHIC sits at the 'sweet spot' for probing the most interesting questions about the quark-gluon plasma and its transition to matter as we know it." The meeting will also feature talks on the planned upgrade of the PHENIX experiment to a new RHIC detector known as sPHENIX, which will have greatly increased capabilities for tracking subatomic interactions. In addition, at least one talk will focus on the scientific rationale for building an Electron-Ion Collider, a proposed future facility that would enable an in-depth exploration of gluons in protons and other nuclei, opening a new frontier in nuclear physics.
Select QM 2017 Highlights from RHIC
Does size really matter?
Discerning differences among heavy quarks
Going with the flow PHENIX will present precision results from its Central Barrel Vertex Detector showing that some heavy quarks are more affected by the QGP than others. The results show that charm quarks lose more energy in the QGP than heavier bottom quarks. With this high statistics data set, PHENIX will now be able to study how the energy-loss is affected by how central, or head-on, the collisions are. PHENIX will also present its first heavy-quark result from the Forward Silicon Vertex Tracker, measuring the total cross section of bottom quarks emerging in the forward and rearward directions in collisions between copper and gold ions.
Learning how particles grow
Tracking high-momentum jets
Taking the QGP's temperature PHENIX's measurements of temperature have relied on tracking photons, particles of light, emitted from the hot matter (think of the glow of an iron bar in a blacksmith's fire, where the color of the light is related to how hot the iron is). But PHENIX's photon data have uncovered something unusual: While collisions initially emit photons equally in all directions, fractions of a second later the emitted photons appear to have a directional preference that resembles the elliptical flow pattern of the perfect liquid QGP. This is intriguing because photons shouldn't interact with the matter-or even be produced in such measurable quantities as the matter produced in the collisions cools and expands. To explore this mystery, PHENIX measured thermal direct photons at different gold-gold collision energies (39, 62, and 200 billion electron volts, or GeV), as well as in the smaller collision system. The results they present will shed light on the sources of these direct photons.
Disentangling the effects of cold nuclear matter
New way to turn down the energy
Related Links Brookhaven National Laboratory Understanding Time and Space
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