Beam-Target Double-Spin Asymmetry $A_{\mathrm{LT}}$ in Charged Pion Production from Deep Inelastic Scattering on a Transversely Polarized ${}^3\mathrm{He}$ Target at $1.4<Q^2<2.7{\mathrm{GeV}}^2$

We report the first measurement of the double-spin asymmetry $A_{\mathrm{LT}}$ for charged pion electroproduction in semi-inclusive deep-inelastic electron scattering on a transversely polarized ${}^3\mathrm{He}$ target. The kinematics focused on the valence quark region, $0.16<x<0.35$ with $1.4<Q^2<2.7{\mathrm{GeV}}^2$. The corresponding neutron $A_{\mathrm{LT}}$ asymmetries were extracted from the measured ${}^3\mathrm{He}$ asymmetries and proton over ${}^3\mathrm{He}$ cross section ratios using the effective polarization approximation. These new data probe the transverse momentum dependent parton distribution function $g_{1T}^q$ and therefore provide access to quark spin-orbit correlations. Our results indicate a positive azimuthal asymmetry for ${\pi }^{-}$ production on ${}^3\mathrm{He}$ and the neutron, while our ${\pi }^{+}$ asymmetries are consistent with zero.

Figure 1

${}^3\mathrm{He}$ $A_{\mathrm{LT}}^{\cos ({\varphi }_h-{\varphi }_S)}$ azimuthal asymmetry plotted against $x$ for positive (top left) and negative (top right) charged pions. The $A_{\mathrm{LL}}$ correction (see text) that was applied and its uncertainty are shown in the bottom panels.

Figure 2

Neutron $A_{\mathrm{LT}}^{\cos ({\varphi }_h-{\varphi }_S)}$ azimuthal asymmetry for positive (left) and negative (right) charged pions vs $x$.