Q2 dependence of the neutron spin structure function g2n at low Q2

Abstract

We present the first measurement of the Q2 dependence of the neutron spin structure function g2n at five kinematic points covering 0.57(GeV/c) 2â‰Q2â‰1.34(GeV/c)2 at xâ‰σ0.2. Though the naive quark-parton model predicts g2=0, nonzero values occur in more realistic models of the nucleon which include quark-gluon correlations, finite quark masses, or orbital angular momentum. When scattering from a noninteracting quark, g2n can be predicted using next-to-leading order fits to world data for g1n. Deviations from this prediction provide an opportunity to examine QCD dynamics in nucleon structure. Our results show a positive deviation from this prediction at lower Q2, indicating that contributions such as quark-gluon interactions may be important. Precision data obtained for g1n are consistent with next-to-leading order fits to world data. © 2005 The American Physical Society.