Bulletin of the American Physical Society
APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011; Anaheim, California
Session Q10: Hadronic Physics II |
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Sponsoring Units: DNP Chair: Simon Capstick, Florida State University Room: Garden 1 |
Monday, May 2, 2011 10:45AM - 10:57AM |
Q10.00001: Charged Pion Multiplicity Below 1.0 GeV/c from the MIPP Experiment Andrew Hart The MIPP experiment is designed to study particle production from several targets, using various beam species and momenta. Using beams of $\pm 58~\mbox{GeV}/c$ pions, kaons, and protons, we present multiplicities of $0.1 - 1.0~\mbox{GeV}/c$ charged pions versus target atomic weight ($A$) for the following targets: liquid hydrogen, beryllium, carbon, aluminum, copper, bismuth, and uranium. We fit $A^{\alpha}$ to these results and present $\alpha$ for each case. In addition, for liquid hydrogen, we present charged pion multiplicities for $\pm 20$ and $\pm 85~\mbox{GeV}/c$ pion, kaon, and proton beam particles, illustrating the dependence on beam momentum. [Preview Abstract] |
Monday, May 2, 2011 10:57AM - 11:09AM |
Q10.00002: Prompt Photon Longitudinal Double Spin Asymmetry in Polarized Proton-Proton Collisions at 200 GeV at STAR Michael Betancourt Over the past decade experiments at RHIC have significantly constrained the polarized gluon distribution function, $\Delta g \left( x, Q^{2} \right)$, with asymmetry measurements of various hadronic final states. While powerful, these hadronic measurements are limited by systematic uncertainties from hadronization and their sensitivity to the gluon polarization is diluted by contributions from the quark polarization. Prompt photon final states admit cleaner and more direct probes of the gluon polarization, limited by the decreased statistics from a smaller cross section and the ability to discriminate the signal from the overwhelming hadronic backgrounds. Mitigating these drawbacks requires the introduction of sophisticated data analysis techniques, efficiently utilizing as much information as possible from the large acceptance electromagnetic calorimetry and tracking provided by the STAR detector and taking full advantage of the collected data. I will present the status of a mid-rapidity prompt photon cross section and longitudinal double spin asymmetry, $A_{\mathrm{LL}}$, analyses using $\sim 14 \mathrm{pb}^{-1}$ of integrated luminosity taken during the 2009 200 GeV running period, using beams averaging $59\%$ longitudinal polarization. [Preview Abstract] |
Monday, May 2, 2011 11:09AM - 11:21AM |
Q10.00003: Measurement of Light Anti-quark Asymmetry in $p+p(d)\rightarrow\mu^++\mu^-$ Drell-Yan Process in Fermilab E-906/SeaQuest Experiment Chiranjib Dutta The Fermilab E-906/SeaQuest experiment will measure the anti-quark structure of the nucleon which eventually will give unique insight into the origin of the sea quarks. The predecessor E866/NuSea experiment showed a clear asymmetry of the ratio $\frac{\bar{d}}{\bar{u}}$ for Bjorken x $<$0.2 while it approaches unity for x$>$0.25, indicating clear deviations from the phenomenological models. The E-906/SeaQuest experiment will measure the Drell-Yan cross section in p-p and p-d scattering and will determine the $\frac{\bar{d}}{\bar{u}}$ asymmetry over 0.04 $<$ x $<$ 0.45, thus extending the available E-866 measurements to a higher x region. The experiment will use the 120 GeV/c proton beam extracted from the Fermilab Main Injector on liquid hydrogen and deuterium targets. A lower beam energy compared to E-866 will produce a factor of almost 50 times more Drell-Yan events in E-906 and hence, a significant improvement in the statistical uncertainty will be achieved. The experiment will start taking data in 2011 and the physics motivation as well as the current status, primarily the design and status of the cryogenic targets will be presented. The expected results from E906/SeaQuest experiment will also be addressed. [Preview Abstract] |
Monday, May 2, 2011 11:21AM - 11:33AM |
Q10.00004: Transverse single spin asymmetries in hadronic gauge boson production Andreas Metz, Jian Zhou Measuring the sign of the Sivers asymmetry in the Drell-Yan process is one of the most important projects for high-energy spin physics. Such a measurement not only would critically test our current understanding of transverse single spin asymmetries in the framework of QCD, but has also far-reaching consequences beyond spin physics. Based on new studies we argue that the same underlying dynamics can be tested in the production of W-bosons in proton-proton collisions. Numerical studies for kinematics at the RHIC will be shown. Moreover, we present results for another spin correlation in the Drell-Yan process which is also complementary to the Sivers effect, but does not rely on the factorization in terms of transverse momentum dependent correlators. [Preview Abstract] |
Monday, May 2, 2011 11:33AM - 11:45AM |
Q10.00005: Studying nucleon structure using an Electron-Ion Collider Thomas Burton The detailed composition of the spin of the nucleon remains unknown. Numerous experiments over the past two decades have shown that the spin of quarks alone cannot account for more than a third of the nucleon's spin. Proton-proton collisions at RHIC suggest a small gluon polarisation, but uncertainties remain large. An Electron-Ion Collider is proposed as future machine for precision studies of nucleon and nuclear structure. It will allow the study of the spin contribution from gluons and quarks, including their flavour decomposition, in heretofore unprecedented precision, and will access a much wider kinematic space than ever before, in particular extending to the currently unmeasured low Bjorken-x sea. The formalism of generalised parton distributions (GPDs), accessible for example via deeply-virtual Compton scattering, promises to allow study of the role of orbital angular momentum in nucleon spin. Furthermore, GPDs will extend understanding of parton distributions beyond the well-known one-dimensional PDFs, accessing three-dimensional structure via the impact parameter distributions of partons. [Preview Abstract] |
Monday, May 2, 2011 11:45AM - 11:57AM |
Q10.00006: ABSTRACT WITHDRAWN |
Monday, May 2, 2011 11:57AM - 12:09PM |
Q10.00007: A Measurement of Neutron Polarization Asymmetries in Photofission of $^{235,238}U$ Using Polarized Gamma Rays at HI$\gamma$S J.M. Mueller, M.W. Ahmed, S.S. Henshaw, H.J. Karwowski, L. Myers, B.A. Perdue, S. Stave, J.R. Tompkins, H.R. Weller, B. Davis, D. Markoff A photofission experiment was performed on $^{235,238}U$ using nearly 100\% linearly polarized, high intensity ($\sim 10^{7} \gamma/s$), and nearly-monoenergetic gamma-ray beams of energies between 5.8 and 7.0 MeV at the High Intensity Gamma-ray Source (HI$\gamma$S). An array of 18 liquid scintillating detectors, located at $55,72,90,107,125,142 ^{\circ}$ in theta and $0,90,180,270 ^{\circ}$ in phi, was used to measure prompt neutron angular distributions. The ratio of prompt neutron yields parallel to the plane of beam polarization to the yields perpendicular to this plane was measured as a function of beam and neutron energies. A ratio of unity was found for $^{235}U$ while a significant ratio ($\sim 3$) was found for $^{238}U$. A phenomenological model of near threshold photofission is being developed in an attempt to explain this large difference for these two isotopes. A simulation, based on our model and using previous measurements of fission fragment angular distributions, is being used to interpret our experimental findings. [Preview Abstract] |
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