Measurement of $q_T$-weighted TSAs in 2015 COMPASS Drell-Yan data

TL;DR

This paper reports on the measurement of $q_T$-weighted transverse spin asymmetries in the 2015 COMPASS Drell-Yan data, providing insights into TMD PDFs and comparing results with SIDIS asymmetries.

Contribution

It presents the first measurement of $q_T$-weighted TSAs in Drell-Yan, offering a new way to access TMD PDFs and compare with SIDIS results.

Findings

$q_T$-weighted TSAs are extracted from COMPASS data.

Results are compared with SIDIS Sivers asymmetry.

Provides new constraints on TMD PDFs.

Abstract

In the polarised Drell-Yan experiment at the COMPASS facility at CERN the beam of negatively-charged pions with 190 GeV/c momentum and intensity about $10^8$ pions/s interacted with transversely polarised NH$_3$ target. Muon pairs produced in Drell-Yan process (DY) were detected. Recently, the first ever Transverse Spin Asymmetries (TSAs) measurement in DY has been presented by COMPASS. A complementary analysis of the TSAs weighted by powers of the dimuon transverse momentum $q_T$ are presented. In the Transverse Momentum Dependent (TMD) PDF formalism, the $q_T$-weighted TSAs can be written in terms of products of the TMD PDFs of two colliding hadrons, unlike the conventional TSAs, which are their convolutions over quarks transverse momenta. The results are compared in a straightforward way with the weighted Sivers asymmetry in the SIDIS process, released by COMPASS in 2016.