Sivers effect and the single spin asymmetry A_N in p(transv. pol.) p --> h X processes

TL;DR

This paper investigates the Sivers effect's role in single spin asymmetries in proton-proton collisions, showing it can explain observed asymmetries up to high transverse momenta.

Contribution

It provides a detailed analysis of Sivers functions from SIDIS data and assesses their impact on A_N in proton-proton collisions within a generalized parton model.

Findings

Sivers functions can account for most features of A_N data.

The Sivers effect explains non-zero A_N at large P_T.

Results support the relevance of transverse momentum dependent factorization.

Abstract

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.