Spin-independent and double-spin cos(phi) asymmetries in semi-inclusive pion electroproduction

We consider the cos(phi) dependence of the longitudinal double-spin asymmetry for charged pion electroproduction in semi-inclusive deep inelastic scattering, emphasizing intrinsic transverse momentum effects. This azimuthal asymmetry allows to measure the cos(phi) moments of the unpolarized and double-spin cross-section, simultaneously. The size of the asymmetry, in the approximation where all twist-3 interaction-dependent distribution and fragmentation functions are set to zero, is estimated for HERMES kinematics; both the spin-independent and the double-spin cos(phi) moments are predicted to be sizeable and negative.