Title

Precision measurement of the neutron spin asymmetries and spin-dependent structure functions in the valence quark region

Publication Date

2004

Journal or Book Title

PHYSICAL REVIEW C

Abstract

We report on measurements of the neutron spin asymmetries A n1,2 and polarized structure functions g n1,2 at three kinematics in the deep inelastic region, with x=0.33 , 0.47, and 0.60 and Q2 =2.7 , 3.5, and 4.8 (GeV/c)2 , respectively. These measurements were performed using a 5.7 GeV longitudinally polarized electron beam and a polarized 3He target. The results for An1 and gn1 at x=0.33 are consistent with previous world data and, at the two higher- x points, have improved the precision of the world data by about an order of magnitude. The new An1 data show a zero crossing around x=0.47 and the value at x=0.60 is significantly positive. These results agree with a next-to-leading-order QCD analysis of previous world data. The trend of data at high x agrees with constituent quark model predictions but disagrees with that from leading-order perturbative QCD (PQCD) assuming hadron helicity conservation. Results for An2 and gn2 have a precision comparable to the best world data in this kinematic region. Combined with previous world data, the moment dn2 was evaluated and the new result has improved the precision of this quantity by about a factor of 2. When combined with the world proton data, polarized quark distribution functions were extracted from the new gn1 / Fn1 values based on the quark-parton model. While results for Δu/u agree well with predictions from various models, results for Δd/d disagree with the leading-order PQCD prediction when hadron helicity conservation is imposed.

DOI

10.1103/PhysRevC.70.065207

Volume

70

Issue

6

Pages

-

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