Quark model analysis of the Sivers function

A formalism is developed aimed at evaluating the Sivers function entering single spin asymmetries. The approach is well suited for calculations which use constituent quark models to describe the structure of the nucleon. A non-relativistic approximation of the scheme is performed to calculate the Sivers function using the Isgur-Karl model. The results we have obtained are consistent with a sizable Sivers effect, with an opposite sign for the u and d flavors. This pattern is in agreement with the one found analysing, in the same model, the impact parameter dependent generalized parton distributions. Although a consistent QCD evolution of the results from the momentum scale of the model to the experimental one is not yet possible, an estimate shows that a reasonable agreement with the available data is obtained once the evolution of the model results is performed.