Beam-spin Asymmetries from Semi-inclusive Pion Electroproduction

The moment of the semi-inclusive deep inelastic scattering (SIDIS) cross section corresponding to a polarized lepton scattering from an unpolarized target is $A_{LU}^{\sin\phi}$. It has been extracted from measurements of beam-spin asymmetries (BSAs) from pion electro-production in SIDIS. Data were taken with the continuous electron beam accelerator facility (CEBAF) Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 5.498 GeV longitudinally polarized electron beam and an unpolarized liquid hydrogen target. All three pion channels ($\pi^+$, $\pi^0$ and $\pi^-$) were measured simultaneously over a large range of kinematics at the intermediate $Q^2$ range ($Q^2 \approx$ 1 - 4.5 $GeV^2$). The moment is measured as functions of $z$, $P_T$, $x$, and $Q^{2}$. $A_{LU}^{\sin\phi}$ is a twist-3 structure providing information about quark-gluon-quark correlations. This new high statistical data will provide an important means of studying the transverse degrees of freedom in the nucleon.