Measurement of single-spin azimuthal asymmetries in semi-inclusive electroproduction of pions and kaons on a longitudinally polarised deuterium target

TL;DR

This paper reports measurements of single-spin azimuthal asymmetries in semi-inclusive electroproduction of pions and kaons on a longitudinally polarised deuterium target, revealing small but significant asymmetries in the azimuthal distributions.

Contribution

It provides the first detailed measurement of azimuthal asymmetries for multiple mesons in deep-inelastic scattering with a longitudinally polarised deuterium target.

Findings

Measured non-zero $ ext{sin}\, ext{phi}$ moments for $\pi^+$, $\pi^-$, $\pi^0$, and $K^+$.

$ ext{sin}\,2 ext{phi}$ moments are consistent with zero for all particles.

Quantified analyzing powers with statistical and systematic uncertainties.

Abstract

Single-spin asymmetries have been measured for semi-inclusive electroproduction of $\pi^+$, $\pi^-$, $\pi^0$ and $K^+$ mesons in deep-inelastic scattering off a longitudinally polarised deuterium target. The asymmetries appear in the distribution of the hadrons in the azimuthal angle $\phi$ around the virtual photon direction, relative to the lepton scattering plane. The corresponding analysing powers in the $\sin \phi$ moment of the cross section are $0.012 \pm 0.002 {(stat.)} \pm 0.002 {(syst.)}$ for $\pi^+$, $0.006 \pm 0.003 {(stat.)} \pm 0.002 {(syst.)}$ for $\pi^-$, $0.021 \pm 0.005 {(stat.)} \pm 0.003 {(syst.)}$ for $\pi^0$ and $0.013 \pm 0.006 {(stat.)} \pm 0.003 {(syst.)}$ for $K^+$. The $\sin 2\phi$ moments are compatible with zero for all particles.