Determination of the proton spin structure functions for 0.05<Q2<5 GeV2 using CLAS

CLAS Collaboration

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44 Scopus citations

Abstract

We present the results of our final analysis of the full data set of g1p(Q2), the spin structure function of the proton, collected using CLAS at Jefferson Laboratory in 2000-2001. Polarized electrons with energies of 1.6, 2.5, 4.2, and 5.7 GeV were scattered from proton targets (NH315 dynamically polarized along the beam direction) and detected with CLAS. From the measured double spin asymmetries, we extracted virtual photon asymmetries A1p and A2p and spin structure functions g1p and g2p over a wide kinematic range (0.05 GeV2<Q2< 5 GeV2 and 1.08 GeV <W< 3 GeV) and calculated moments of g1p. We compare our final results with various theoretical models and expectations, as well as with parametrizations of the world data. Our data, with their precision and dense kinematic coverage, are able to constrain fits of polarized parton distributions, test pQCD predictions for quark polarizations at large x, offer a better understanding of quark-hadron duality, and provide more precise values of higher twist matrix elements in the framework of the operator product expansion.

Original languageEnglish
Article number065208
JournalPhysical Review C
Volume96
Issue number6
DOIs
StatePublished - Dec 27 2017

Funding

We would like to acknowledge the outstanding efforts of the staff of the Accelerator and the Physics Divisions at Jefferson Lab that made this experiment possible. This work was supported in part by the US Department of Energy and the National Science Foundation, the Italian Istituto Nazionale di Fisica Nucleare, the French Centre National de la Recherche Scientifique, the French Commissariat à l’Energie Atomique, the Emmy Noether grant from the Deutsche Forschungs Gemeinschaft, the United Kingdom’s Science and Technology Facilities Council, and the National Research Foundation of Korea. The Jefferson Science Associates (JSA) operates the Thomas Jefferson National Accelerator Facility for the United States Department of Energy under Contract No. DE-AC05-06OR23177. This work was supported in part by the US Department of Energy and the National Science Foundation, the Italian Istituto Nazionale di Fisica Nucleare, the French Centre National de la Recherche Scientifique, the French Commissariat a l'Energie Atomique, the Emmy Noether grant from the Deutsche Forschungs Gemeinschaft, the United Kingdom's Science and Technology Facilities Council, and the National Research Foundation of Korea. The Jefferson Science Associates (JSA) operates the Thomas Jefferson National Accelerator Facility for the United States Department of Energy under Contract No. DE-AC05-06OR23177.

FundersFunder number
Not addedST/P004458/1
Deutsche Forschungs Gemeinschaft
Jefferson Science Associates
Thomas Jefferson National Accelerator Facility for the United States Department of EnergyDE-AC05-06OR23177
National Science Foundation1615146, 1506172, 1505615
U.S. Department of Energy
Science and Technology Facilities CouncilST/J000175/1, ST/G008582/1
National Research Foundation of Korea
Centre National de la Recherche Scientifique
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
National Science Foundation
Istituto Nazionale di Fisica Nucleare

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