Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session 1WB: Workshop on New Results in Spin Physics from Polarized Proton Beams at RHIC/New Results in Heavy Ions |
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Chair: Richard Hollis and Aneta Iordanova, University of California, Riverside Room: Plaza II |
Wednesday, October 24, 2012 8:30AM - 9:00AM |
1WB.00001: QCD and RHIC Spin Physics Invited Speaker: Zhongbo Kang Understanding the nucleon structure is of fundamental importance to science. The exploration of the internal structure of the nucleon in terms of quarks and gluons (partons), the degrees of freedom of Quantum Chromodynamics (QCD), has been and still is at the frontier of high energy nuclear physics research. Concurrent advances in the experimental use of high energy scattering processes and theoretical breakthroughs in understanding ``asymptotic freedom'' and developing the perturbation theory of strong interactions have provided a way of mapping out the internal landscape of protons and neutrons. In this talk, we will present how RHIC spin program has made significant contributions in understanding the proton structure, particularly the spin structure of the proton. We will discuss the tremendous theoretical progress in recent years towards understanding both the longitudinal and transverse spin phenomena observed at RHIC experiments. We start with the original goals of RHIC spin program, briefly report what we have learned so far on the proton spin structure. We then review the most recent developments on theoretical formalism, particularly on those so-called transverse-momentum-dependent factorization. We emphasize how spin has become a useful tool to study QCD factorization and evolution, and to probe the three-dimensional motion of the partons inside the proton. We end our talk with a brief outlook on the future opportunities and challenges. [Preview Abstract] |
Wednesday, October 24, 2012 9:00AM - 9:30AM |
1WB.00002: Recent Results from the RHIC Longitudinal Spin Program Invited Speaker: Renee Fatemi The high energy, highly polarized proton beams at the Relativistic Heavy Ion Collider (RHIC) provide a unique opportunity to significantly expand our knowledge about the spin structure of the proton and the role of Quantum Chromodynamics in hadronic collisions. The PHENIX and STAR experiments have utilized the 100 GeV longitudinally polarized beams to measure inclusive pion and jet double spin asymmetries, providing the first significant constraints on the gluon contribution $(\Delta{G})$ to the spin of the proton. As the spin program matures, and the integrated luminosity increases, the experimental focus naturally shifts toward correlation channels, which allow a more precise mapping of the gluon helicity distribution as a function of the gluon momentum fraction $x_g$. Measurements of inclusive and correlation channels at 250 GeV beam energies will extend experimental sensitivities to lower $x$ gluons, reducing the total error on $\Delta{G}$. The advent of polarized proton collisions at $\sqrt{s} = 500$ GeV, first demonstrated in the 2009 RHIC run, has also allowed STAR and PHENIX to embark on a program to constrain the flavor separated anti-sea quark helicity distributions ($\Delta\bar{u},\Delta\bar{d}$) via measurements of single spin asymmetries of the leptonic decay of $W^{-(+)}$ bosons. The data collected during a very productive 2012 RHIC run will allow the experiments to substantially increase the statistical power and expand the kinematic reach of the initial 2009 measurements. Recent results, projected sensitivities and future detector upgrades for the RHIC $\Delta{G}$ and W programs will be discussed. [Preview Abstract] |
Wednesday, October 24, 2012 9:30AM - 10:00AM |
1WB.00003: Transverse spin physics in proton-proton collisions at RHIC Invited Speaker: K. Oleg Eyser Transverse single spin asymmetries have gained an increased interest over the past years. They were originally expected to be very small as calculated in perturbative QCD at high energies and transverse momenta, but they have persisted at very sizable amplitudes in forward kinematics. Higher twist effects can explain these transverse asymmetries in a collinear approach complementary to transverse momentum dependent distribution functions in the initial state and fragmentation functions in the final state. Transverse asymmetries therefore not only enable us to complete our knowledge about parton distribution functions of the nucleon but also allow for fundamental tests of QCD, involving questions of universality and factorization. The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory is the world's only polarized proton collider with center-of-mass energies up to 500 GeV and transverse polarizations of 55{\%} and more of each proton beam. It provides unique opportunities to study the spin structure in hadronic systems and opens new kinematic regions compared to deep inelastic scattering. This talk will summarize the recent results from the PHENIX and STAR experiments and discuss their implications on the different theoretical regimes. [Preview Abstract] |
Wednesday, October 24, 2012 10:00AM - 10:30AM |
1WB.00004: Entering the Electronic Age at RHIC: eRHIC Invited Speaker: Christine Aidala After enjoying a stream of thought-provoking results from the Relativistic Heavy Ion Collider (RHIC) for more than a decade, the QCD community is now contemplating the compelling physics that RHIC, as the most versatile hadron collider in the world, will be well positioned to explore beyond the program planned for upgrades already in progress. As the fields that RHIC set out to investigate have advanced and evolved, new questions and directions have arisen at the frontiers of QCD, and we have exciting opportunities before us to continue to confront the challenges and surprises of strong interactions into the next decade and beyond. The addition of an electron beam to what is already such a flexible collider would create a formidable machine offering unprecedented and very broad opportunities for the study of QCD in hadrons and nuclei, allowing full exploitation of the complementary nature and interplay of electron-hadron and hadron-hadron collisions. Such a facility would for example allow us to perform precision spatial and momentum mapping of the structure of the nucleons and nuclei of everyday matter, study the physics of strong color fields in nuclei, explore in detail the effects of soft scales on hard partonic processes, and confront the question of the transition from asymptotically free quarks and gluons to final-state hadrons observable in the laboratory. Some of the prospects for an initial eRHIC program will be presented. [Preview Abstract] |
Wednesday, October 24, 2012 10:30AM - 10:45AM |
1WB.00005: COFFEE BREAK
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Wednesday, October 24, 2012 10:45AM - 11:15AM |
1WB.00006: Dileptons at RHIC Invited Speaker: Zhangbu Xu This invited talk provides an overview of the results of the dilepton production at RHIC from PHENIX and STAR experiments. Sources of dileptons interesting to us are decay products from the virtual photon from QGP thermal radiation and in-medium vector meson. Dominant background sources are photon conversion in detector material, heavy-flavor decays, Dalitz decays from mesons and vector-meson decays in vacuum. Over the last decade, both experiments have been constantly improving their detector capabilities and analysis techniques. In addition, RHIC has produced Au+Au collisions with good statistics for dilepton physics from top SPS to top RHIC energies. I will present the recent results on dilepton yields as a function of beam energy, invariant mass, pair transverse momentum and collision reaction plane. Future measurements with combination of electrons and muons enable us to assess the contribution from correlated charm pair at the intermediate mass range and to subtract this ``irreducible'' background. I will discuss the specific properties of strongly interacting medium these measurements are sensitive to. [Preview Abstract] |
Wednesday, October 24, 2012 11:15AM - 11:45AM |
1WB.00007: Quarkonium production in heavy-ion collisions at the LHC Invited Speaker: Torsten Dahms Recent results on charmonium and bottomonium production and suppression in PbPb collisions at $\sqrt{s_{NN}}$ = 2.76~TeV at the LHC will be reviewed. Furthermore, these results will be compared to theoretical models and measurements at lower center-of-mass energies. [Preview Abstract] |
Wednesday, October 24, 2012 11:45AM - 12:15PM |
1WB.00008: Jet measurements at the LHC Invited Speaker: Wei Li I will review the latest results from the heavy ion program on high-$p_T$ jet physics at the LHC. The high luminosity PbPb run at the LHC in 2012 has significantly extended the capability of studying high-$p_T$ rare processes produced in the heavy ion collisions. New results from ALICE, ATLAS and CMS experiments will be presented. This includes detailed precision measurements on dijet energy imbalance, jet shape and fragmentation pattern, jet nuclear modification factor, jet-track correlations, as well as path-length dependence of jet quenching. [Preview Abstract] |
Wednesday, October 24, 2012 12:15PM - 12:45PM |
1WB.00009: sQGP - A theorist's point of view Invited Speaker: Sangyon Jeon By now, there is not any doubt that the relativistic heavy ion colliders - RHIC and LHC - have created the long-sought Quark-Gluon Plasma (QGP). This new state of matter presents us many surprises. The most surprising one may be the fact that despite the deconfinement, quarks and gluons inside QGP seem to interact very strongly. In this talk, I will try to cover experimental facts such as minimal shear viscosity and strong jet quenching that points to sQGP (strongly interacting QGP), and how theories and models based on many-body QCD are trying to understand those facts. A particular emphasis will be on the big picture understanding of sQGP and its evolution in heavy ion collisions in connection to many-body QCD. [Preview Abstract] |
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