Phys. Rev. C 70, 065207 (2004) [25 pages]Precision measurement of the neutron spin asymmetries and spin-dependent structure functions in the valence quark regionReceived 13 May 2004; published 27 December 2004 We report on measurements of the neutron spin asymmetries A1,2n and polarized structure functions g1,2n 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 A1n and g1n 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 A1n 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 A2n and g2n have a precision comparable to the best world data in this kinematic region. Combined with previous world data, the moment d2n 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 g1n∕F1n 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. © 2004 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevC.70.065207
DOI:
10.1103/PhysRevC.70.065207
PACS:
13.60.Hb, 24.85.+p, 25.30.−c
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