Single spin asymmetries in charged pion production from semi-inclusive deep inelastic scattering on a transversely polarized He3 target at Q2=1.4-2.7GeV2

Abstract

We report the first measurement of target single spin asymmetries in the semi-inclusive He3(e,e′π±)X reaction on a transversely polarized target. The experiment, conducted at Jefferson Lab using a 5.9 GeV electron beam, covers a range of 0.16<x<0.35 with 1.4<Q2<2.7GeV2. The Collins and Sivers moments were extracted from the azimuthal angular dependence of the measured asymmetries. The π± Collins moments for He3 are consistent with zero, except for the π+ moment at x=0.35, which deviates from zero by 2.3σ. While the π- Sivers moments are consistent with zero, the π+ Sivers moments favor negative values. The neutron results were extracted using the nucleon effective polarization and measured cross section ratios of proton to He3, and are largely consistent with the predictions of phenomenological fits and quark model calculations. © 2011 American Physical Society.