The Beam Single Spin Asymmetry in Semi-inclusive Deep Inelastic Scattering

We study the beam single spin asymmetry in semi-inclusive hadron production in deep inelastic scattering in at order 1/Q. There are two competing contributions: the leading order transverse momentum dependent parton distribution $h_1^\perp(x,k_\perp)$ convoluted with chiral-odd fragmentation function $\hat e(z)$, and the chiral-odd distribution function $e(x)$ convoluted with Collins fragmentation function $H_1^\perp(z,k'_\perp)$. We estimate this asymmetry and compare with the experimental measurements from CLAS and HERMES collaborations.