Beam-Spin Azimuthal Asymmetries in Pion Electroproduction at HERMES

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.