Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session E3: New Results on the Spin Structure of the NucleonInvited
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Sponsoring Units: DNP Chair: Volker Burkert, Thomas Jefferson National Accelerator Laboratory Room: Ballroom B |
Saturday, April 16, 2016 3:30PM - 4:06PM |
E3.00001: Nucleon transverse spin structure in the valence quark region: Probing color forces Invited Speaker: Zein-Eddine Meziani The first direct observation that protons are not elementary objects and the discovery that their constituents, dubbed “partons”, are point-like particles made use of elastic and deep inelastic (DIS) scattering of electrons off protons, respectively. With the advent of quantum chromodynamics (QCD), the modern theory of strong interactions, partons were identified as quarks and gluons and an intensive theoretical effort is still underway to grasp the full consequences of this theory. Recently scattering experiments at Jefferson Lab using a 6 GeV polarized electron beam and polarized targets at high luminosity have allowed us to delve deeper into the role of partons dynamics in the nucleon (proton and neutron). These studies of dynamics in the valence quark region are helping us unravel the rich but elusive structure of the confined building blocks of matter and impacting our understanding of the non-perturbative aspects of QCD through comparisons with lattice QCD and models. I will present recent results of measurements of the average color electric and magnetic forces acting on the struck quark in a proton, due to the remnant ”di-quark” as it start its journey to emerge as a hadron. A flavor separation of the color force acting on the up and down quarks is carried out by combining measurements on polarized protons and neutrons. I will conclude by describing the planned measurements with the 12 GeV upgrade of Jefferson Lab to complete our picture of nucleon transverse spin structure in the valence region. [Preview Abstract] |
Saturday, April 16, 2016 4:06PM - 4:42PM |
E3.00002: Transverse Spin at RHIC Invited Speaker: Xiaorong Wang In recent years, there has been exciting development in both experimental and theoretical studies of transverse spin asymmetries in polarized p+p and and DIS collisions. As a unique polarized proton-proton collider, Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) provides a unique opportunity to investigate the novel physics mechanisms that cause the large single spin asymmetry at the forward rapidity. Both PHENIX and STAR experiments have been studying the transverse spin asymmetries with a variety of final state particles in different kinematic regimes since 2006. Especially, recent theoretical development on scattering a polarized probe on the saturated nuclear may provide a unique way to probe the gluon and quark TMDs. RHIC successfully ran polarized p+Au collisions in 2015. We will expect to have new results from polarized d+Au to compare with existing results from p+p collision to extend our understanding of QCD. Further more, In 2015, PHENIX installed MPC-ex calorimeter at very forward region to measure direct photon $A_N$ and STAR installed Roman Pots to study the diffractive events in polarized p+p and p+Au collisions. The recent results on transverse polarized p+p and p+Au collisions from both PHENIX and STAR experiments will be presented in this talk. I will also briefly discuss the possibility for the transverse Spin program at future experiments sPHENIX and forward sPHENIX at RHIC. [Preview Abstract] |
Saturday, April 16, 2016 4:42PM - 5:18PM |
E3.00003: Studies of chiral-odd GPDs using pseudoscalar meson production at Jefferson Lab Invited Speaker: Andrey Kim The quark-gluon dynamics manifests itself in a set of non-perturbative functions describing all possible spin-spin and spin-orbit correlations. The Generalized Parton Distributions (GPDs) carry information not only on the longitudinal momentum but also on the transverse position of partons, providing rich and direct information on the orbital motion of quarks. The analysis of experimental measurements on hard exclusive pseudoscalar meson electroproduction is a key to constrain the chiral-odd GPD parameterizations. Combination of measurements on unpolarized cross-sections and spin asymmetries with a longitudinally polarized beam and both unpolarized and longitudinally polarized proton targets for $\pi^0$ and $\eta$ electroproduction will provide a detailed test for existing model calculations and allow for the first insight into the quark flavor decomposition of the underlying chiral-odd GPDs. In this talk, we present an overview of the current status and some future measurements of hard exclusive processes and extraction of underlying GPDs at Jefferson Lab. [Preview Abstract] |
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