Beam single spin asymmetry of neutral pion production in semi-inclusive   deep inelastic scattering
  We study the beam spin asymmetry $A_{LU}^{\sin\phi_h}$ in semi-inclusive $\pi^0$ electroproduction contributed by the T-odd twist-3 distribution function $g^\perp(x,k_T^2)$. We calculate this transverse momentum dependent distribution function for the $u$ and $d$ quarks inside the proton in a spectator model including the scalar and the axial-vector diquark components. Using the model results, we estimate the asymmetry $A_{LU}^{\sin\phi_h}$ in the $e p \rightarrow e^\prime \pi^0 X$ process in which the lepton beam is longitudinally polarized. The model prediction is compared with the data measured by the CLAS and the HERMES Collaborations and it is found that our numerical results agree with experimental data reasonably. Especially, our results can well describe the CLAS data at the region where the Bjorken $x$ and the pion transverse momentum is not large. We also make a prediction on the asymmetry $A_{LU}^{\sin\phi_h}$ in a $\pi^0$ electroproduction at CLAS12 using the same model calculation. 
Wenjuan Mao, Zhun Lu
hep-ph hep-ex