Bulletin of the American Physical Society
2016 Fall Meeting of the APS Division of Nuclear Physics
Volume 61, Number 13
Thursday–Sunday, October 13–16, 2016; Vancouver, BC, Canada
Session FF: Mini-symposium on Cold Nuclear Matter from Fixed-Target Energies to the LHC IMini-Symposium
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Chair: Ramona Vogt, LLNL and UC Davis Room: Pavilion Ballroom A |
Friday, October 14, 2016 4:00PM - 4:36PM |
FF.00001: QCD Factorization Approach to Cold Nuclear Matter Effects Invited Speaker: Jianwe Qiu Cold nuclear matter effects exist in all high energy collisions involving identified nucleus (or nuclei). They have been manifested in very significant ways in e-A and p-A, as well as A-A collisions, where the cold nuclear effect is a part of the initial condition which plays a critical role in determining the outcome of heavy ion collisions. In this talk, I will discuss if it is possible to consistently calculate or extract the cold nuclear effect, the advantage and limitation of QCD factorization approach, and the predictive power or the testability of the QCD calculations. [Preview Abstract] |
Friday, October 14, 2016 4:36PM - 4:48PM |
FF.00002: Physics with (un)polarized Proton-Nucleus Collisions at STAR/RHIC K. Oleg Eyser While there has been tremendous progress in nuclear experiments and theory over the past few decades, we are still left with many open questions regarding the partonic structure of nucleons and nuclei. These include the nature of the nucleon spin itself, transverse momentum dependent parton densities from light to heavy nuclei and their correlation with spin, as well as the role of saturated strong gluon fields and their subsequent regime of non-linear QCD dynamics. The kinematic coverage of world data from semi-inclusive deep inelastic scattering and fixed target hadronic experiments is so far too limited to provide answers to these questions. In 2015, RHIC has successfully collided polarized proton beams with heavy ions enabling unique measurements of various observables for the first time at a center of mass energy of 200 GeV (per nucleon). Among the observables are transverse spin asymmetries and the suppression of direct photons when compared to proton-proton collisions. We will discuss the prospects of these and other possible measurements and how they will complement the physics programs at LHC and a future electron-ion collider. [Preview Abstract] |
Friday, October 14, 2016 4:48PM - 5:00PM |
FF.00003: Overview and Status of the SeaQuest Experiment Larry Donald Isenhower SeaQuest (E906) is a Fermilab fixed target experiment and has been running since December 2013. It has made significant progress towards its goal of extending measurements made by earlier Fermilab Drell-Yan (D-Y) experiments, E866 and E772. A description will be given of the effort that went into building this new high-mass, high-rate capability di-muon spectrometer with entirely new target, trigger, and DAQ systems. These were integrated into detector systems which are new or recycled from other experiments. A completely new beam operation mode had to be developed by Fermilab that would allow a slow extraction of the beam for SeaQuest over four seconds while not disturbing the fast extraction mode for neutrino running. A beam Cherenkov detector was built that could run at the necessary 53 MHz rate to monitor each beam pulse and produce a beam veto for large proton bunches. After commissioning, SeaQuest has made steady progress on the amount of data recorded. The current status will be shown, along with expectations for the next year. Many challenges have been overcome by this collaboration in order to produce data for analysis. A broad range of physics results will be the result of this effort as well as a number of possible future experiments. [Preview Abstract] |
Friday, October 14, 2016 5:00PM - 5:12PM |
FF.00004: Light quark flavor asymmetry in the nucleon sea Arun Tadepalli SeaQuest E906 is an experiment aimed at studying the anti-quark distributions in the nucleon and nuclei. The experiment uses a 120 GeV proton beam extracted from the Main Injector at Fermilab to collide with various targets of hydrogen, deuterium, carbon, iron and tungsten to study a variety of physics topics. It takes advantage of the Drell-Yan process to probe the nucleon sea structure. In the Drell-Yan process, a quark from one hadron annihilates with an anti-quark from another hadron, producing a virtual photon which eventually decays into a dilepton pair. The SeaQuest forward spectrometer is optimized for detecting such di-muons. Comparison of Drell-Yan cross-section ratios of liquid hydrogen and deuterium allows SeaQuest to probe the $\overline{d}(x)/\overline{u}(x)$ ratio up to a region of ~0.45 in Bjorken-x, a region which hasn't been explored yet. Preliminary analysis of data sets will be presented in the talk. [Preview Abstract] |
Friday, October 14, 2016 5:12PM - 5:24PM |
FF.00005: Constraining the Sea Quark Distributions Through W$^\pm$ Cross Section Ratio Measurements at STAR Matthew Posik Over the past several years parton distribution functions (PDFs) have become more precise, however there are still regions where more data are needed to help constrain global PDF extractions. One such distribution is the sea quark distribution near the valence region (Bjorken-x $\approx$ 0.1 - 0.3), in particular the $\bar{d}/\bar{u}$ distribution which seems to suggest possible non-perturbative effects playing a role in this region. The charged W cross section ratio (W$^+$/W$^-$) is sensitive to the unpolarized $u,\;d,\;\bar{u},$ and $\bar{d}$ quark distributions at large $Q^2$ (set by the $W$ mass). Through proton-proton collisions, the STAR experiment at RHIC, is well equipped to measure the e$^{\pm}$ leptonic decays of W$^{\pm}$ bosons in the mid-rapidity range $\left(|\eta| \leq 1 \right)$ at $\sqrt{s}$ = 500/510 GeV. At these kinematics STAR is sensitive to quark distributions near Bjorken-x of 0.1. RHIC runs from 2011 through 2013 have collected about 350 pb$^{-1}$ of integrated luminosity. Presented here are preliminary results for the 2011-2012 W charged cross section ratios, which contribute about 100 pb$^{-1}$ to the total data collected, and an update on the 2013 charged W cross section analysis, which contributes about 250 pb$^{-1}$ to the total data collected. [Preview Abstract] |
Friday, October 14, 2016 5:24PM - 5:36PM |
FF.00006: $\phi$ Meson Measurements at Forward/Backward Rapidity at RHIC with PHENIX Detector Xiaochun He Given the relatively small hadronic interaction cross section, $\phi$ meson production provide a unique and complimentary method for exploring the hot and dense medium properties created in the relativistic heavy ion collisions. In this talk, a summary of the $\phi$ measurements at forward and backward rapidities in p+p, d+Au, Cu+Au collisions in the PHENIX experiment at RHIC will be given. [Preview Abstract] |
Friday, October 14, 2016 5:36PM - 5:48PM |
FF.00007: Pinning Down Low-x Physics With the MPC-EX at RHIC-PHENIX Natha Grau The evolution of the nuclear parton distribution functions (nPDFs) are an important ingredient to understanding results from heavy ion collisions. A silicon-tungsten preshower detector, the MPC-EX, was added to the front of the existing MPC electromagnetic calorimeter in the PHENIX detector for the 2016 $d$+Au run. Situated at 3<|$\eta$|<4 and full azimuth, the MPC-EX will enhance the capabilities of measuring photons and $\pi^0$s originating from collisions at large $Q^2$ and low-$x$ partons in the gold beam. In this talk I will overview the status of the detector in the 2016 d+Au and discuss the current state of analysis and how it is expected to answer open questions regarding the evolution of nPDFs. [Preview Abstract] |
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