Author/Authors :
HERMES Collaboration، نويسنده , , A. Airapetian، نويسنده , , N. Akopov، نويسنده , , Z. Akopov، نويسنده , , M. Amarian، نويسنده , , E.C. Aschenauer، نويسنده , , H. Avakian، نويسنده , , R. Avakian، نويسنده , , A. Avetissian، نويسنده , , E. Avetissian، نويسنده , , P. Bailey، نويسنده , , V. Baturin، نويسنده , , C. Baumgarten، نويسنده , , M. Beckmann ، نويسنده , , S. Belostotski، نويسنده , , S. Bernreuther، نويسنده , , N. Bianchi، نويسنده , , H. B?ttcher، نويسنده , , A. Borissov، نويسنده , , O. Bouhali، نويسنده , , et al.، نويسنده ,
Abstract :
A single-spin asymmetry in the distribution of exclusively produced π+ mesons azimuthally around the virtual photon direction relative to the lepton scattering plane has been measured for the first time in deep-inelastic scattering of positrons off longitudinally polarized protons. Integrated over the experimental acceptance, the sinφ moment of the polarization asymmetry of the cross section is measured to be −0.18±0.05(stat.)±0.02(syst.). The asymmetry is also studied as a function of the relevant kinematic variables, and its magnitude is found to grow with decreasing x and increasing −t and vanish at t→tmin (where x is the Bjorken scaling variable and t is the squared four-momentum transferred to the nucleon).
