Sivers function in light-cone quark model and azimuthal spin asymmetries in pion electroproduction

Abstract

We perform a calculation of Sivers function in a light-cone SU(6) quark-diquark model with both scalar diquark and vector diquark spectators. We derive the transverse momentum dependent light-cone wave function of the proton by taking into account the Melosh-Wigner rotation. By adopting one-gluon exchange, we obtain a non-vanishing Sivers function of $down$ quark from interference of proton spin amplitudes. We analyze the $\frac{|P_{h\perp }|}{M}$ weighted Sivers asymmetries in ${\pi }^{+}$, ${\pi }^{-}$ and ${\pi }^0$ electroproduction off transverse polarized proton target, averaged and not averaged by the kinematics of HERMES experiment.

Comments: 17 LaTex pages, 2 figures. Final version for journal publication