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 |P h⊥| M weighted Sivers asymmetries in π +, π − and π 0 electroproduction off transverse polarized proton target, averaged and not averaged by the kinematics of HERMES experiment.