Single Spin Asymmetries in Charged Pion Production from Semi-Inclusive Deep Inelastic Scattering on a Transversely Polarized ${}^3\mathrm{He}$ Target at $Q^2=1.4–2.7{\mathrm{GeV}}^2$

We report the first measurement of target single spin asymmetries in the semi-inclusive ${}^3\mathrm{He}(e,e^{\prime }{\pi }^{\pm })X$ 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 $1.4<Q^2<2.7{\mathrm{GeV}}^2$. The Collins and Sivers moments were extracted from the azimuthal angular dependence of the measured asymmetries. The ${\pi }^{\pm }$ Collins moments for ${}^3\mathrm{He}$ are consistent with zero, except for the ${\pi }^{+}$ moment at $x=0.35$, which deviates from zero by $2.3\sigma$. While the ${\pi }^{-}$ Sivers moments are consistent with zero, the ${\pi }^{+}$ Sivers moments favor negative values. The neutron results were extracted using the nucleon effective polarization and measured cross section ratios of proton to ${}^3\mathrm{He}$, and are largely consistent with the predictions of phenomenological fits and quark model calculations.

Figure 1

The extracted Collins or Sivers moments on ${}^3\mathrm{He}$ are shown together with uncertainty bands (see text) for both ${\pi }^{+}$ and ${\pi }^{-}$ electroproduction.

Figure 2

The extracted neutron Collins and Sivers moments with uncertainty bands for both ${\pi }^{+}$ and ${\pi }^{-}$ electroproduction. See text for details.