A quark model analysis of the Sivers function

TL;DR

This paper presents a formalism for calculating the Sivers function using constituent quark models, specifically applying it to the Isgur-Karl model, and finds results consistent with experimental data and theoretical expectations.

Contribution

It introduces a new formalism for evaluating the Sivers function within constituent quark models, including a non-relativistic reduction and application to the Isgur-Karl model.

Findings

Sivers function shows a sizable effect with opposite signs for u and d quarks.

Results are consistent with the impact parameter dependent GPDs.

The Burkardt Sum Rule is largely satisfied.

Abstract

We develop a formalism to evaluate the Sivers function. The approach is well suited for calculations which use constituent quark models to describe the structure of the nucleon. A non-relativistic reduction of the scheme is performed and applied to the Isgur-Karl model of hadron structure. The results obtained are consistent with a sizable Sivers effect and the signs for the u and d flavor contributions turn out to be opposite. This pattern is in agreement with the one found analyzing, in the same model, the impact parameter dependent generalized parton distributions. The Burkardt Sum Rule turns out to be fulfilled to a large extent. We estimate the QCD evolution of our results from the momentum scale of the model to the experimental one and obtain reasonable agreement with the available data.