Study of the sign change of the Sivers function from STAR Collaboration W/Z production data

TL;DR

This paper investigates the sign change of the Sivers function in Drell-Yan processes using recent STAR Collaboration data on W/Z production, comparing it with SIDIS data to test a fundamental QCD prediction.

Contribution

It provides the first analysis of the Sivers function sign change in W/Z production data from STAR, combining new SIDIS extractions and critical data assessment.

Findings

Evidence supporting the sign change hypothesis

Quantitative comparison between SIDIS and Drell-Yan Sivers functions

Assessment of the significance of STAR data in this context

Abstract

Recent data on the transverse single spin asymmetry $A_N$ measured by the STAR Collaboration for $p^\uparrow \, p \to W^\pm/Z^0 \, X$ reactions at RHIC allow the first investigation of the Sivers function in Drell-Yan processes and of its expected sign change with respect to SIDIS processes. A new extraction of the Sivers functions from the latest SIDIS data is performed and a critical assessment of the significance of the STAR data is attempted.