Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session X2: From Valence to Glue: Current Status and Future Directions |
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Sponsoring Units: DNP Chair: Abhay Deshpande, State University of New York at Stony Brook Room: Hyatt Regency Jacksonville Riverfront Grand 1 |
Tuesday, April 17, 2007 10:45AM - 11:21AM |
X2.00001: The Landscape of Polarized Sea and Glue Invited Speaker: The origin of the intrinsic spin of the nucleon is a topic of active experimental and theoretical research. In the 1980's the European Muon Collaboration used a high energy beam of polarized muons from the CERN SPS and a target with polarized protons to make polarized deep-inelastic scattering measurements covering an extensive kinematic range. The observed spin-dependent cross-section, or the inclusive spin structure function of the proton, was found to be smaller than expected from constituent quark models. The data, when combined with information from baryon octet $\beta$-decays, lead to the conclusion that the total quark spin constitutes about 20\% of the spin of the nucleon. This nonintuitively small total quark spin contribution to the nucleon spin has, to a large extent, motivated the spin physics programs at CERN, DESY, SLAC, JLAB, and RHIC, and continues to be a strong motivation for further research. The gluon spin contribution to the nucleon spin and the role of the polarized sea are natural questions and form main goals of the current generation of experiments. This presentation will focus on recent advances and discuss prospects for the future. [Preview Abstract] |
Tuesday, April 17, 2007 11:21AM - 11:57AM |
X2.00002: Towards Precision Proton Tomography Invited Speaker: Generalized Patron Distributions (GPDs) contain a wealth of information about hadron structure. Mapping the GPDs will allow one, for the first time, to construct ``tomographic'' images of the nucleon's charge and quark helicity distributions in transverse impact parameter space. GPDs can be accessed through lepton scattering processes such as Deeeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP). Different facilities world --wide including HERMES at HERA, CLAS and Hall-A at JLab and COMPASS at CERN have measurements of hard exclusive processes as one of their main focuses of research. In this talk we present an overview of the latest developments in the study of GPDs and newly released results will be also presented. The talk will conclude with prospects of the GPD program at existing and planned machines. [Preview Abstract] |
Tuesday, April 17, 2007 11:57AM - 12:33PM |
X2.00003: Probing Dense Gluonic Matter in Nuclei at High Energies Invited Speaker: High energy collisions involving nuclei provide a unique opportunity to study QCD in the strong-field limit. At high energies the Lorentz contraction of the nucleus results in the longitudinal overlap of low-momentum gluons producing a strong, coherent gluon field with large occupation numbers, characteristic of classical fields. In the context of parton distribution functions, the large gluon density in the contracted nucleus is expected to make non-linear recombination effects in the evolution of the gluon distribution, $g(x,Q^2)$, at low $x$ dominant below some resolution scale, $Q^2 < Q_s^2$. This ``satuation'' of the low-x parton distributions is a direct consequence of unitarity in the strong-field limit of QCD. Results from HERA suggest that saturation is already seen in deep-inelastic scattering on the proton, and extrapolations of the extracted saturation scale, $Q_s$ to large nuclei suggest that saturation may play an important role at RHIC in the production of forward jets in deuteron-Au collisions and in limiting the multiplicity of produced particles in Au+Au collisions. I will present the results of such measurements from RHIC and will discuss future measurements at RHIC, the LHC and a future electron-ion collider that will provide new insight on the strong-field limit of QCD. [Preview Abstract] |
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