Beam-spin asymmetries from semi-inclusive pion electroproduction

We have measured the moment A(LU)(sin phi) corresponding to the polarized electron beam-spin asymmetry in semi-inclusive deep inelastic scattering. A(LU)(sin phi) is a twist-3 quantity providing information about quark-gluon correlations. Data were taken with the CLAS Spectrometer 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 within the virtuality range Q(2) approximate to 1.0- 4.5 GeV2. The observable was measured with better than 1% statistical precision over a large range of z, P-T, x(B), and Q(2), which permits comparison with several reaction models. The discussed measurements provide an upgrade in statistics over previous measurements, and serve as the first evidence for the negative sign of the pi(-) sin phi moment.