  The single spin asymmetry A_N, for large P_T single inclusive particle
production in p(transv. pol.) p collisions, is considered within a generalised
parton model and a transverse momentum dependent factorisation 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 non
zero A_N up to surprisingly large P_T values.
