Single Spin Asymmetries in Charged Pion Production from Semi-Inclusive Deep Inelastic Scattering on a Transversely Polarized $^3$He Target

TL;DR

This paper presents the first measurement of target single spin asymmetries in semi-inclusive deep inelastic scattering on a transversely polarized helium-3 target, providing insights into the spin structure of the neutron.

Contribution

It introduces the first experimental measurement of Collins and Sivers moments in semi-inclusive scattering on a transversely polarized $^3$He target, extending understanding of nucleon spin asymmetries.

Findings

$ ext{π}^+$ Collins moment at $x=0.34$ deviates from zero by 2.3$\sigma$

$ ext{π}^-$ Sivers moments are consistent with zero

$ ext{π}^+$ Sivers moments favor negative values

Abstract

We report the first measurement of target single spin asymmetries in the semi-inclusive $^3{He}(e,e'\pi^\pm)X$ reaction on a transversely polarized target. The experiment, conducted at Jefferson Lab using a 5.9 GeV electron beam, covers a range of 0.14 $< x <$ 0.34 with 1.3 $<Q^2<$ 2.7 GeV$^2$. The Collins and Sivers moments were extracted from the azimuthal angular dependence of the measured asymmetries. The extracted $\pi^\pm$ Collins moments for $^3$He are consistent with zero, except for the $\pi^+$ moment at $x=0.34$, 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 the measured cross section ratio of proton to $^3$He, and are largely consistent with the predictions of phenomenological fits and quark model calculations.