Bulletin of the American Physical Society
2007 Annual Meeting of the Division of Nuclear Physics
Volume 52, Number 10
Wednesday–Saturday, October 10–13, 2007; Newport News, Virginia
Session BB: Mini-Symposium on the Global Analysis of Spin-Dependent Parton Distributions I |
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Chair: Abhay Deshpande, SUNY, Stony Brook Room: Newport News Marriott at City Center Grand Salon III |
Thursday, October 11, 2007 2:00PM - 2:36PM |
BB.00001: Towards a Global QCD Analysis of Helicity-Dependent Parton Densities Invited Speaker: A solid understanding of the theoretical framework and its phenomenological inputs has been crucial for the success of perturbative QCD in the past and continues to be vital for ongoing and future nuclear and high-energy research programs. Taking single-inclusive hadron production as an example, I will briefly discuss recent progress in extracting fragmentation functions from data. Next, I will review the current status of spin-dependent parton densities and outline the steps towards a global QCD analysis. [Preview Abstract] |
Thursday, October 11, 2007 2:36PM - 2:48PM |
BB.00002: Polarized Semi-Inclusive DIS measurements at Jefferson Lab Peter Bosted, Harut Avakian Longitudinally polarized electrons with energies
of 4.2 and 5.7 GeV and longitudinally polarized
proton and deuteron targets were used
to measure the double spin asymmetries in
semi-inclusive
deep-inelastic scattering. Scattered electrons and electro-produced
pions where detected in the CEBAF Large Acceptance Spectrometer at
Jefferson Lab. The kinematic range covered is:
$0.3 |
Thursday, October 11, 2007 2:48PM - 3:00PM |
BB.00003: Di-Jet Cross Section and Longitudinal Double Spin Asymmetry Measurements with Event Kinematics Constraints in Polarized Proton-Proton Collisions at 200 GeV at STAR Tai Sakuma The polarized gluon distribution in the proton, Delta G, is of particular interest to the STAR Spin program. While initial studies have focused on inclusive pion and jet analyses, the recent improvements in RHIC luminosity and polarization enable di-jet analysis as the first correlation analysis to constrain initial event kinematics. With it's large acceptance electromagnetic calorimetry and tracking system, STAR is well suited for these measurements. We report the status of the measurements of di-jet cross section at mid-rapidity for RHIC 2005 run and A{\_}LL within the pseudorapidity range from -1 to +2 for RHIC 2006 run. [Preview Abstract] |
Thursday, October 11, 2007 3:00PM - 3:12PM |
BB.00004: Spin Structure of the Deuteron - New Results from CLAS Nevzat Guler The EG1B experiment, which was carried out at Jefferson Lab using the CLAS detector, measured double polarization asymmetries in the nucleon resonance region and above ( $1.08 GeV < W < 3.0 GeV$ ). We used a longitudinally polarized electron beam of various energies incident on longitudinally polarized proton and deuteron targets. The large kinematic coverage of the experiment ( $0.05 GeV^2 < Q^2 < 5.0 GeV^2$ ) will help us to understand the spin structure of the nucleon especially in the transition region between the hadronic degrees of freedom and the quark-gluon degrees of freedom. In this presentation new preliminary results on $A_1$ and $A_2$ for the deuteron will be shown. [Preview Abstract] |
Thursday, October 11, 2007 3:12PM - 3:24PM |
BB.00005: Double Longitudinal Spin Asymmetry for Inclusive Hadron Production in 200 GeV Polarized p+p Collisions STAR Alan Hoffman A primary goal of the STAR-spin program is the measurement of the gluon polarization (delta g) in the proton. The STAR detector, with its large-acceptance tracking and calorimetery, provides a uniquely suited environment for asymmetry measurements in a number of different final-state channels in polarized p+p collisions. These asymmetries will provide significant contributions to a global analysis of delta g. We present here the most recent measurements of the double longitudinal spin asymmetries (A$_{LL})$ for the inclusive production of both neutral and charged pions at mid-rapidity. These asymmetries are compared to NLO pQCD calculations for different polarization scenarios and are used to provide constraints on delta g. Charged pions are of particular interest as they are sensitive to the sign of delta g. Results and continuing analyses are presented from RHIC runs 5 and 6. [Preview Abstract] |
Thursday, October 11, 2007 3:24PM - 3:36PM |
BB.00006: Accessing the Gluon Polarization in the Proton through the Measurement of the Double Helicity Asymmetry in Neutral Pion Production in Polarized Proton Collisions at PHENIX Kieran Boyle A primary goal of the RHIC Spin program is to measure the gluon spin contribution ($\Delta G$) to the spin of the proton through the measurement of double helicity asymmetries ($A_{LL} $) in polarized proton collisions. Pions are abundantly produced in proton-proton collisions and so are a good candidate for a high statistics analysis. The PHENIX EMCal has good energy resolution and high granularity which, when used with a high energy photon trigger, yield a substantial $\pi^0$ sample over a wide range in transverse momentum ($p_T$). The 2005 and 2006 polarized proton runs (at $\sqrt{s}=200$ GeV) saw large increases in luminosity ($L$) and polarization ($P$) compared to previous runs, resulting in a high figure of merit ($P^4 L$). $\pi^0$ $A_{LL}$ from 2005 and 2006 are precise enough to be sensitive to $\Delta G$. Results from 2005 and 2006 for $\pi^0$ $A_{LL}$ at mid rapidity will be shown. [Preview Abstract] |
Thursday, October 11, 2007 3:36PM - 3:48PM |
BB.00007: Constraints on Gluon Polarization in the Proton from PHENIX Double Helicity Asymmetry Data. Alexander Bazilevsky PHENIX experiment at RHIC has collected significant amount of data on longitudinal double spin asymmetry ($A_{LL}$) for different particle production in polarized proton collisions, which is sensitive to the gluon polarization ($\Delta G$) in the proton. We discuss a simple approach to constrain $\Delta G$ from PHENIX $\pi^0$ $A_{LL}$ data through the comparison with NLO pQCD calculations that incorporate a model of gluon polarization. Limitations of this approach as well as an opportunity to include other channels will be discussed. [Preview Abstract] |
Thursday, October 11, 2007 3:48PM - 4:00PM |
BB.00008: Inclusive $\pi^{0}$ Production in Polarized pp Collisions using the STAR Endcap Calorimeter Jason Webb The two-spin helicity asymmetry for inclusive $\pi^{0}$ production in polarized pp collisions can provide constraints on the gluon contribution to the spin of the proton with sensitivity comparable to that attainable with full jet reconstruction [1]. In 2006, the STAR experiment accumulated $\approx 6 pb^{-1}$ of data with beams longitudinally polarized ($\bar{P}\approx 60\%$) at the Relativistic Heavy Ion Collider. Measurements of $A_{LL}(\pi^0)$ in the range $1 < \eta < 2$ provide information about a different mix of partonic subprocesses and are subject to different experimental uncertainties than mid-rapidity jet measurements, providing an important cross check. Status of the analysis of $A_{LL}(\pi^{0})$ measured using the STAR Endcap Calorimeter [2] is discussed. \newline \newline [1] B. Jager, M. Stratmann and W. Vogelsang, Phys. Rev. {\bf D} 70, 034010 (2004) [arXiv:hep-ph/0404057]. \newline [2] K. H. Ackermann et al. [STAR Collaboration], Nucl. Instrum. Meth. A 499, 624 (2003). [Preview Abstract] |
Thursday, October 11, 2007 4:00PM - 4:12PM |
BB.00009: Neutral Pion Longitudinal Double Spin Asymmetry Measurement at Forward Rapidity with the PHENIX Muon Piston Calorimeter Aaron Veicht The PHENIX experiment at RHIC commissioned a new forward calorimeter during the 2006 polarized proton run, the Muon Piston Calorimeter (MPC). The MPC is a PbWO$_{4}$ based electromagnetic calorimeter covering $3.1<|\eta|< 3.7$ in pseudo rapidity and 2$\pi$ in azimuthal angle. One of the main goals of the PHENIX experiment is to contribute to solving the ``proton spin crisis" by determining the gluon spin contribution to the proton's total spin. This can be done through measurements of the longitudinal double spin asymmetry ($A_{LL}$). Neutral pions produced at the rapidity of the MPC extend the momentum fraction $x$ of the proton sampled, allowing for a measurement of the $\pi^{0}$~$A_{LL}$ in a previously unexplored kinematic region at the PHENIX experiment --- a region where quark-gluon interactions dominate so that the sign of the gluon helicity can be directly measured in $A_{LL}$. In this talk I will present the status from the analysis of the neutral pion $A_{LL}$ using the 2006 $\sqrt{s} = 62$~GeV data. [Preview Abstract] |
Thursday, October 11, 2007 4:12PM - 4:24PM |
BB.00010: Constraints on $\Delta G$ through Longitudinal Double Spin Asymmetry Measurements of Inclusive Jet Production in Polarized p+p Collisions at 200 GeV Murad Sarsour The STAR experiment at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory uses polarized pp collisions at a center of mass energy of $\sqrt{s} = 200$ GeV to determine the polarized gluon distribution in the proton via spin asymmetry measurements. The inclusive jet channel is particularly robust due to its large cross-sections and relative independence from fragmentation functions. Data were collected during 2006, at sampled luminosity of $\sim$\,6 pb$^{-1}$, with 60\% beam polarization. We present run 2006 analysis progress for the double longitudinal spin asymmetry for inclusive jet production at mid-rapidity, along with results from run 2005. Comparisons to theoretical calculations using deep-inelastic scattering parameterization for gluon polarization in the nucleon are also presented. [Preview Abstract] |
Thursday, October 11, 2007 4:24PM - 4:36PM |
BB.00011: Longitudinal Double Spin Asymmetries of Di-Hadron Production at PHENIX in pp Collisions at $\sqrt{s} = 200$ GeV John Koster The PHENIX detector, located at Brookhaven National Laboratory's Relativistic Heavy Ion Collider, measures longitudinal double spin asymmetries ($A_{LL}$) with the goal to determine the gluon spin contribution to the proton spin. The current suite of measurements at RHIC rely on inclusive jet or inclusive hadron kinematics and are successfully determining the gluon spin contribution at moderate values of Bjorken x. Historically, low x contributions were critical in the measurement of the quark spin contribution. This talk will present the current status of a di-hadron measurement which exploits the kinematics of asymmetric collisions to probe gluons at low x. The measurement selects events with two neutral pions, one at mid-rapidity and the second at forward rapidity. A new PHENIX electromagnetic calorimeter and the existing calorimetry at mid-rapidity make this measurement possible. [Preview Abstract] |
Thursday, October 11, 2007 4:36PM - 4:48PM |
BB.00012: Parameterization of the eta fragmentation functions from world e+e- and p+p data Christine Aidala, Joseph Seele, Marco Stratmann, Werner Vogelsang Despite the relatively large production cross section of the eta meson and the facility with which it can be detected and identified experimentally, as yet no parameterization of the eta fragmentation functions has been made available in the literature. The present work seeks to parameterize the eta fragmentation functions using world data from e+e- as well as proton-proton collisions. The data and methods used and the current status will be discussed. [Preview Abstract] |
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