Transverse target single-spin asymmetry in inclusive electroproduction of charged pions and kaons

Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the Hermes experiment. The asymmetries were studied as a function of the azimuthal angle ψ   about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum PTPT relative to the direction of the incident beam, and the Feynman variable xFxF. The sin ψ   amplitudes are positive for π+π+ and K+K+, slightly negative for π−π− and consistent with zero for K−K−, with particular PTPT but weak xFxF dependences. Especially large asymmetries are observed for two small subsamples of events, where also the scattered electron was recorded by the spectrometer.