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

Abstract

Single-spin asymmetries have been measured for semi-inclusive electroproduction of $π^+$, $π^-$, $π^0$ 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 $ϕ$ around the virtual photon direction, relative to the lepton scattering plane. The corresponding analysing powers in the $\sin ϕ$ moment of the cross section are $0.012 \pm 0.002 {(stat.)} \pm 0.002 {(syst.)}$ for $π^+$, $0.006 \pm 0.003 {(stat.)} \pm 0.002 {(syst.)}$ for $π^-$, $0.021 \pm 0.005 {(stat.)} \pm 0.003 {(syst.)}$ for $π^0$ and $0.013 \pm 0.006 {(stat.)} \pm 0.003 {(syst.)}$ for $K^+$. The $\sin 2ϕ$ moments are compatible with zero for all particles.