Precise Measurements of Beam Spin Asymmetries in Semi-Inclusive $\pi^0$   production
  We present studies of single-spin asymmetries for neutral pion electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV polarized electrons from an unpolarized hydrogen target, using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. A substantial $\sin \phi_h$ amplitude has been measured in the distribution of the cross section asymmetry as a function of the azimuthal angle $\phi_h$ of the produced neutral pion. The dependence of this amplitude on Bjorken $x$ and on the pion transverse momentum is extracted with significantly higher precision than previous data and is compared to model calculations. 
M. Aghasyan, H. Avakian, P. Rossi, E. De Sanctis, D. Hasch, M.   Mirazita, D. Adikaram, M.J. Amaryan, M. Anghinolfi, H. Bagh...
hep-ex