Beam spin asymmetry in semi-inclusive electroproduction of a hadron pair

Understand

A first measurement of the longitudinal beam spin asymmetry ALU in the semi-inclusive electroproduction of pairs of charged pions is reported.

• ALU is a higher-twist observable and offers the cleanest access to the nucleon twist-3 parton distribution function e(x).
• Data have been collected in the Hall-B at Jefferson Lab by impinging a 5.498 GeV electron beam on a liquid-hydrogen target, and reconstructing the scattered electron and the pion pair with the CLAS detector.
• One-dimensional projections of the sin(phiR) moments of ALU are extracted for the kinematic variables of interest in the valence quark region.