Sivers effect and the single spin asymmetry A_N in p ^↑p→hX processes

The single spin asymmetry A_N, for large P_T single inclusive particle production in p^↑p collisions, is considered within a generalized parton model and a transverse momentum dependent factorization scheme. The focus is on the Sivers effect and the study of its potential contribution to A_N, based on a careful analysis of the Sivers functions extracted from azimuthal asymmetries in semi-inclusive deep inelastic scattering processes. It is found that such Sivers functions could explain most features of the A_N data, including some recent STAR results which show the persistence of a nonzero A_N up to surprisingly large P_T values.