Investigating the origins of transverse spin asymmetries at RHIC

TL;DR

This paper explores the potential origins of transverse spin asymmetries in hadron collisions, proposing a chiral-odd T-odd distribution function with transverse momentum dependence as a key factor, and models its implications for RHIC measurements.

Contribution

It introduces a novel explanation for spin asymmetries using a specific distribution function and relates unpolarized and polarized observables in Drell-Yan processes at RHIC.

Findings

Proposes a chiral-odd T-odd distribution function model.

Links unpolarized and polarized Drell-Yan asymmetries.

Provides a complete set of azimuthal asymmetries involving T-odd functions.

Abstract

We discuss possible origins of transverse spin asymmetries in hadron-hadron collisions and propose an explanation in terms of a chiral-odd T-odd distribution function with intrinsic transverse momentum dependence, which would signal a correlation between the transverse spin and the transverse momentum of quarks inside an unpolarized hadron. We will argue that despite its conceptual problems, it can account for single spin asymmetries, for example in p + p(transversely polarized) -> pion + X, and at the same time for the large cos(2 phi) asymmetry in the unpolarized Drell-Yan cross section, which still lacks understanding. We use the latter asymmetry to arrive at a crude model for this function and show explicitly how it relates unpolarized and polarized observables in the Drell-Yan process, as could be measured with the proton-proton collisions at RHIC. Moreover, it would provide an alternative method of accessing the transversity distribution function h_1. For future reference we also list the complete set of azimuthal asymmetries in the unpolarized and polarized Drell-Yan process at leading order involving T-odd distribution functions with intrinsic transverse momentum dependence.