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 HG: Hadron Physics III |
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Chair: Kijun Park, Thomas Jefferson National Accelerator Facility Room: Surf |
Friday, October 26, 2012 8:30AM - 8:42AM |
HG.00001: ABSTRACT WITHDRAWN |
Friday, October 26, 2012 8:42AM - 8:54AM |
HG.00002: Measurement of the Transverse Single Spin Asymmetry $A_{N}$ in Polarized Proton-Proton Elastic Collisions at $\sqrt {s}$ = 200 GeV Donika Plyku The STAR experiment at RHIC is equipped with insertion devices (Roman Pots) that allow detectors to be moved close to the beam for the measurement of protons at very small scattering angles. This setup, together with the unique capability of RHIC to collide spin-polarized proton beams, allows STAR to study both unpolarized and spin-dependent proton-proton $(pp)$ elastic scattering. Silicon strip detectors installed inside the Roman Pots, measure tracks of protons scattered diffractively at very small angles. In a dedicated run with special beam optics during the 2009 RHIC run, the experiment collected about 20M elastic events with transversely polarized proton beams at $\sqrt {s}$ = 200 GeV and four-momentum transfer squared $(t)$ range of $ 0.003 $\ $ $GeV$^{2}/c^{2} \le |t| \le 0.035 $\ $ $GeV$^{2}/c^{2} $, where, due to the Coulomb Nuclear Interference (CNI), a measurable single spin asymmetry arises. In this talk, we report on a high precision measurement of the transverse single spin asymmetry $A_{N}$ at $\sqrt {s}$ = 200 GeV. The measured $A_{N}$ and its $t$-dependence are consistent with the absence of a hadronic spin-flip amplitude. [Preview Abstract] |
Friday, October 26, 2012 8:54AM - 9:06AM |
HG.00003: Transverse single-spin asymmetry in heavy-flavor production in $pp$ collisions at $\sqrt{s}$ = 200 GeV Feng Wei Transverse single-spin asymmetries provide valuable information about the spin structure of the nucleon. At RHIC energies, heavy-flavor production is dominated by gluon-gluon fusion. The transverse single-spin asymmetry in heavy-flavor production originates from the Sivers effect (due to the initial state correlation between the internal transverse momentum of the parton and the transverse spin of the nucleon) instead of the Collins effect (the final state interaction of a transversely polarized quark fragmentation into a hadron) since the gluon has no transversity. The measurement of transverse single-spin asymmetry of single muons from heavy flavor decay at RHIC serves as a clean probe and would provide important information on the gluon Sivers function. In 2008 and 2012, the PHENIX experiment has collected 5.2 and 9.2 $pb^{-1}$ integrated luminosity in transversely polarized $pp$ collisions at $\sqrt{s}$ = 200 GeV with a polarization of $46\%$ and $52\%$ respectively. The status of the analysis of transverse single-spin asymmetries of single muons from heavy flavor decay at forward-rapidity will be presented. [Preview Abstract] |
Friday, October 26, 2012 9:06AM - 9:18AM |
HG.00004: Analyzing Power for Forward Jet Production in Polarized Proton Collisions at $\sqrt{s}$=500 GeV Chris Perkins AnDY is an experiment at RHIC whose goal is to measure the analyzing power for Drell-Yan production. Tests were done during $\sqrt{s}$=500 GeV polarized proton operations in RHIC run 11 with a model of the AnDY apparatus in place. The primary detector components were left/right symmetric hadron calorimeter (HCal) modules that spanned the pseudorapidity interval $2.4<\eta<4.0$. An integrated luminosity of 6.5 / pb with average beam polarization of 52\% was primarily sampled by a jet trigger, consisting of a threshold applied to a HCal module sum. The energy in HCal was calibrated by observing the photon pairs from neutral pion decay. The degree to which the HCal has comparable response for incident hadrons relative to incident photons or electrons was studied in simulation, and is still undergoing investigation in the data. Multiple methods of jet reconstruction have been applied to the data. The energy dependence of the forward jet analyzing power will be reported. [Preview Abstract] |
Friday, October 26, 2012 9:18AM - 9:30AM |
HG.00005: Forward di-muon spin asymmetries in PHENIX Jin Huang Di-muon pairs, which are produced from J/$\Psi$ decay and the Drell-Yan process in high energy longitudinally polarized proton-proton collisions, provide insight into the proton spin structure. J/$\Psi$ mesons are predominantly produced through gluon-gluon fusion and therefore provide unique information about the gluon polarization. At the same time the spin asymmetries of the Drell-Yan process are sensitive to the sea-quark polarization at small-x. Forward di-muon production ($1.2<|\eta|<2.4$) is being studied in the PHENIX experiment at RHIC. High statistics di-muon measurements were carried out in the most recent run 2012 (Run12) at $\sqrt{s}=510$ GeV in p+p collisions. The new Forward Silicon Vertex Detector (FVTX), enabled us to explore the Drell-Yan process in detail for the first time at RHIC. The current status of di-muon asymmetry analysis using the PHENIX Run12 data will be presented in this talk. [Preview Abstract] |
Friday, October 26, 2012 9:30AM - 9:42AM |
HG.00006: The Dijet Cross-section Measurement of Polarized Proton-Proton Collision at $\sqrt s =$ 500 GeV Grant Webb The STAR Spin program aims to measure the gluon helicity distribution $\Delta g(x)$ in the proton, which remains highly unconstrained at small momentum fractions $x_B < 0.05$. Dijet reconstruction in polarized proton collisions at $\sqrt s = 500$ GeV will extend these constraints by sampling lower x gluons while also providing more precise information about the partonic kinematics. This contribution will present studies of various jet algorithms and works toward the first measurement of the dijet cross-section from $\sim$ 10 pb$^{-1}$ of data from $\sqrt s = 500$ GeV data taken in 2009. [Preview Abstract] |
Friday, October 26, 2012 9:42AM - 9:54AM |
HG.00007: Di-jet Measurements at Forward Rapidity Utilizing the Endcap Electromagnetic Calorimeter (EEMC) at the STAR Detector Brian Page One of the main goals of the STAR spin program is to determine
the spin-dependent gluon distribution, $\Delta g(x)$, of the proton. To date, the most stringent constraints on $\Delta g(x)$ from STAR have come from inclusive jet measurements, which access a partonic Bjorken-x range of $0.05 |
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