We report on measurements of the neutron spin asymmetries A n 1,2 and polarized structure functions g n 1,2 at three kinematics in the deep inelastic region, with x = 0.33, 0.47 and 0.60 and Q 2 = 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 3 He target. The results for A n 1 and g n 1 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 A n 1 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 A n 2 and g n 2 have a precision comparable to the best world data in this kinematic region. Combined with previous world data, the moment d n 2 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 g n 1 /F n 1 values based on the quark parton model. While results for ∆u/u agree well with predictions from various models, results for ∆d/d disagree with the leading-order pQCD prediction when hadron helicity conservation is imposed.
We report new measurements of the ratio of the electric form factor to the magnetic form factor of the neutron, G n E /G n M , obtained via recoil polarimetry from the quasielastic 2 H( e, e ′ n) 1 H reaction at Q 2 values of 0.45, 1.13, and 1.45 (GeV/c) 2 with relative statistical uncertainties of 7.6 and 8.4% at the two higher Q 2 points, which were not reached previously via polarization measurements. Scale and systematic uncertainties are small.
We have measured the neutron spin asymmetry A(n)(1) with high precision at three kinematics in the deep inelastic region at x=0.33, 0.47, and 0.60, and Q(2)=2.7, 3.5, and 4.8 (GeV/c)(2), respectively. Our results unambiguously show, for the first time, that A(n)(1) crosses zero around x=0.47 and becomes significantly positive at x=0.60. Combined with the world proton data, polarized quark distributions were extracted. Our results, in general, agree with relativistic constituent quark models and with perturbative quantum chromodynamics (PQCD) analyses based on the earlier data. However they deviate from PQCD predictions based on hadron helicity conservation.
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