Nucleon partonic spin structure to be explored by the unpolarized Drell-Yan program of COMPASS experiment at CERN

TL;DR

The COMPASS experiment at CERN aims to explore the nucleon's partonic spin structure by measuring angular distributions in unpolarized Drell-Yan processes, focusing on the Lam-Tung relation violation and transverse spin correlations.

Contribution

This study proposes using the COMPASS experiment's measurements to investigate the nucleon's transverse spin structure and the origin of Lam-Tung relation violation.

Findings

Expected high-statistics data from 2015 run.

Potential to clarify the role of Boer-Mulders functions.

Insights into partonic transverse spin correlations.

Abstract

The observation of the violation of Lam-Tung relation in the $\pi N$ Drell-Yan process triggered many theoretical speculations. The TMD Boer-Mulders functions characterizing the correlation of transverse momentum and transverse spin for partons in unpolarized hadrons could nicely account for the violation. The COMPASS experiment at CERN will measure the angular distributions of dimuons from the unpolarized Drell-Yan process over a wide kinematic region and study the beam particle dependence. Significant statistics is expected from a successful run in 2015 which will bring further understanding of the origin of the violation of Lam-Tung relation and of the partonic transverse spin structure of the nucleon.