Towards a first estimate of the gluon Sivers function from $A_N$ data in $pp$ collisions at RHIC

TL;DR

This paper estimates the gluon Sivers function using precise RHIC $A_N$ data in $pp$ collisions, combining it with known quark Sivers functions within a generalized parton model to improve understanding of gluon transverse momentum effects.

Contribution

It provides the first estimate of the gluon Sivers function from RHIC data, integrating recent experimental results with existing quark Sivers information within a generalized parton model.

Findings

First estimate of gluon Sivers function from RHIC data

Updated bounds on gluon Sivers distribution

Integration of quark and gluon Sivers functions in analysis

Abstract

Within a generalized parton model approach, with inclusion of spin and intrinsic transverse momentum effects, we show how the latest, highly precise, midrapidity data on the transverse single spin asymmetry measured in $pp\to\pi^0\, X$ by the PHENIX Collaboration at RHIC [1], can be used to get a first estimate on the still poorly known gluon Sivers distribution. To this end we also adopt the present information on the quark Sivers functions, as extracted from semi-inclusive deeply inelastic scattering data. This analysis updates a previous study by some of us where a first bound on this distribution was obtained [2].