Azimuthal distributions of pions inside jets at RHIC

TL;DR

This paper analyzes azimuthal asymmetries of leading pions inside jets in high-energy proton-proton collisions at RHIC, using a transverse momentum dependent approach to disentangle spin effects and test Sivers function universality.

Contribution

It introduces a method to separate Sivers and Collins effects in azimuthal asymmetries and examines the role of gauge-invariant initial and final state interactions.

Findings

Disentangled Sivers and Collins contributions to asymmetries.

Proposed a test for Sivers function universality.

Analyzed impact of gauge-invariant interactions on asymmetries.

Abstract

We evaluate the azimuthal asymmetries for the distributions of leading pions inside a jet, produced in high-energy proton-proton collisions, in kinematic configurations currently under active investigation at RHIC. Adopting a transverse momentum dependent approach, which assumes the validity of a perturbative QCD factorization scheme and takes into account all the spin and intrinsic parton motion effects, we show how the main mechanisms underlying these asymmetries, namely the Sivers and the Collins effects, can be disentangled. Furthermore, we consider the impact of color-gauge invariant initial and final state interactions and suggest a method for testing the universality properties of the Sivers function for quarks.