Flavor, transverse momentum, and azimuthal dependence of charged pion multiplicities in SIDIS with 10.6 GeV electrons

Abstract

Measurements of SIDIS multiplicities for $\pi^+$ and $\pi^-$ from proton and deuteron targets are reported on a grid of hadron kinematic variables $z$, $P_{T}$, and $\phi^{*}$ for leptonic kinematic variables in the range $0.3<x<0.6$ and $3<Q^2<5$ GeV$^2$. Data were acquired in 2018-2019 at Jefferson Lab Hall C with a 10.6~GeV electron beam impinging on 10-cm-long liquid hydrogen and deuterium targets. Scattered electrons and charged pions were detected in the HMS and SHMS spectrometers, respectively. The multiplicities were fitted for each bin in $(x,~Q^2,~z,~P_{t})$ to extract the $\phi^{*}$ independent $M_0$ and the azimuthal modulations $\langle \cos(\phi^{*}) \rangle$ and $\langle \cos(2\phi^{*}) \rangle$. The $P_t$-dependence of the $M_0$ results was found to be remarkably consistent for the four cases studied: $ep\rightarrow e \pi^+ X$, $ep\rightarrow e \pi^- X$, $ed\rightarrow e \pi^+ X$, $ed\rightarrow e \pi^- X$ over the range $0<P_t<0.4$ GeV, as were the multiplicities evaluated near $\phi^* = 180^\circ$ over the extended range $0<P_t<0.7$ GeV. The Gaussian widths of the $P_t$-dependence exhibit a quadratic increase with $z$. The $\cos(\phi^{*})$ modulations were found to be consistent with zero for $\pi^+$, in agreement with previous world data, while the $\pi^-$ moments were, in many cases, significantly greater than zero. The $\cos(2\phi^{*})$ modulations were found to be consistent with zero. The higher statistical precision of this dataset compared to previously published data should allow improved determinations of quark transverse momentum distributions and higher twist contributions.