Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session G3: Invited Session: Spin Structure of the Nucleon at Short and Long Distances |
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Sponsoring Units: DNP Chair: Sebastian Kuhn, Old Dominion University Room: Plaza E |
Sunday, April 14, 2013 8:30AM - 9:06AM |
G3.00001: Spin structure functions of the proton and the neutron at low to moderate Q$^2$ Invited Speaker: Nevzat Guler The physics program with CLAS at the Jefferson Lab has collected a large amount of data on the spin structure functions of the nucleon by using polarized electron beam directed on polarized NH$_3$ and ND$_3$ targets. In these experiments, the virtual photon asymmetry $A_1$ and the spin structure function $g_1$ were measured with an unprecedented precision in a large kinematic range of 0.01 GeV$^2$ $<$ Q$^2$ $<$ 6.0 GeV$^2$ and 1.08 GeV $< W <$ 3.0 GeV. The data help us to better understand the spin structure of the nucleon, especially in the transition region between hadronic and quark-gluon degrees of freedom. Therefore, it will be possible to put limits on quark-hadron duality, test pQCD predictions for the quark polarization at large $x$, perform more precise calculations of higher-twist matrix elements in the framework of the Operator Product Expansion and get a glimpse of A$_1$ at high $x$. In addition, using available proton and deuteron data together and utilizing a new unfolding technique, the spin structure functions for the neutron in the resonance region are extracted. [Preview Abstract] |
Sunday, April 14, 2013 9:06AM - 9:42AM |
G3.00002: Probing the Spin Structure of the Nucleon: New Experimental Results on $d_2$ and $A_1$ for both Neutron and Proton from JLab Invited Speaker: Brad Sawatzky The last several years of Jefferson Lab's 6~GeV physics program saw a wealth of nucleon spin structure measurements run across several Halls. In particular, E06-014 (``$d_2^n$") in Hall A (polarized neutron), and E07-003 (``SANE") in Hall C (polarized proton) took advantage of significant advances in target design and new/upgraded large solid angle detector packages to run precision measurements of neutron and proton spin structure functions over the region $0.2 < x < 0.8$ and $2.5 < Q^2 < 6.5$\,GeV$^2/c^2$. Of note, the SSF $g_2$ and associated higher twist reduced matrix element $d_2$ are fundamentally coupled to the quark-gluon interactions and transverse momentum of the quarks in the nucleon, and are among the cleanest higher twist observables we can access. New data on $g_1$, $g_2$, spin asymmetries $A_1$ and $A_2$, and the $d_2$ moment for both the neutron and proton will be presented, and future measurements that exploit JLab's 12~GeV upgrade will be touched on. [Preview Abstract] |
Sunday, April 14, 2013 9:42AM - 10:18AM |
G3.00003: First JAM results on the determination of polarized parton distributions Invited Speaker: Pedro Jimenez-Delgado The Jefferson Lab Angular Momentum (JAM) collaboration is a new initiative aimed to the study of the angular-momentum-dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic scattering will be presented and compared with previous determinations from other groups. Different aspects of global QCD analysis will be discussed, including effects due to nuclear structure, higher twist, and target-mass corrections, as well as the impact of different data selections. [Preview Abstract] |
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