Beam Single-Spin Asymmetry in Semi-Inclusive Deep Inelastic Scattering
  We calculate, in a model, the beam spin asymmetry in semi-inclusive jet production in deep inelastic scattering. This twist-3, $T$-odd observable is non-zero due to final state strong interactions. With reasonable choices for the parameters, one finds an asymmetry of several percent, about the size seen experimentally. We present the result both as an explicit asymmetry calculation and as a model calculation of the new transverse-momentum dependent distribution function $g^\perp$. 
Andrei V. Afanasev and Carl E. Carlson