Precise determination of the deuteron spin structure at low to moderate Q2 with CLAS and extraction of the neutron contribution

Abstract

© 2015 American Physical Society. We present the final results for the deuteron spin structure functions obtained from the full data set collected in 2000-2001 with Jefferson Lab's continuous electron beam accelerator facility (CEBAF) using the CEBAF large acceptance spectrometer (CLAS). Polarized electrons with energies of 1.6, 2.5, 4.2, and 5.8 GeV were scattered from deuteron (15ND3) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double-spin asymmetry, the virtual photon absorption asymmetry A1d and the polarized structure function g1d were extracted over a wide kinematic range (0.05GeV2<Q2<5GeV2 and 0.9GeV<W<3GeV). We use an unfolding procedure and a parametrization of the corresponding proton results to extract from these data the polarized structure functions A1n and g1n of the (bound) neutron, which are so far unknown in the resonance region, W<2 GeV. We compare our final results, including several moments of the deuteron and neutron spin structure functions, with various theoretical models and expectations, as well as parametrizations of the world data. The unprecedented precision and dense kinematic coverage of these data can aid in future extractions of polarized parton distributions, tests of perturbative QCD predictions for the quark polarization at large x, a better understanding of quark-hadron duality, and more precise values for higher-twist matrix elements in the framework of the operator product expansion.