Beam-Spin Azimuthal Asymmetries in Pion Electroproduction at HERMES

TL;DR

This paper reports measurements of single beam-spin azimuthal asymmetries in pion electroproduction during semi-inclusive deep inelastic scattering at HERMES, providing insights into nucleon structure and spin-momentum correlations.

Contribution

It presents the first detailed measurement of azimuthal asymmetries in pion electroproduction at HERMES, including their dependence on kinematic variables and comparison with theoretical models.

Findings

Measured $ ext{sin}\phi$ azimuthal asymmetries for $\pi^+,\pi^-, ext{and}\pi^0$

Observed dependence of asymmetries on Bjorken $x$, $z$, and $P_T$

Results agree with certain theoretical model predictions

Abstract

We present the measurement of Single Beam-Spin Azimuthal Asymmetries in pion electroproduction off hydrogen in semi-inclusive deep inelastic scattering (SIDIS). The measurement was made using the HERMES spectrometer with an internal gas target and the polarized 27.6 GeV electron(positron) beam of HERA using the data taken during the years 1996-2000. The $\sin\phi$ modulation of the azimuthal asymmetry was measured for semi-inclusive $\pi^+,\pi^-$ and $\pi^0$. The dependence of the asymmetry on the Bjorken $x$, pion relative ($z$) and transverse ($P_T$) momentum is presented. Results are compared to theoretical model calculation.