paper

Precision Measurement of the Neutron Spin Asymmetries and Spin-dependent Structure Functions in the Valence Quark Region

arXiv:nucl-ex/0405006 · doi:10.1103/PhysRevC.70.065207

Abstract

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

A typing error in A_\parallel(3He) at x=0.47 in Table VII of Phys. Rev. C has been noticed and corrected

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