Transverse single spin asymmetry in the Drell-Yan process

TL;DR

This paper re-evaluates the transverse single spin asymmetry in Drell-Yan processes using twist-3 collinear factorization, ensuring gauge invariance and finding results that differ from previous literature, highlighting the importance of the asymmetry's sign.

Contribution

It provides a new calculation of the transverse single spin asymmetry in Drell-Yan, confirming gauge invariance and revealing discrepancies with earlier results.

Findings

Final asymmetry expression differs from previous literature

Gauge invariance of the calculation is verified

Sign of the asymmetry is as crucial as the Sivers asymmetry

Abstract

We revisit the transverse single spin asymmetry in the angular distribution of a Drell-Yan dilepton pair. We study this asymmetry by using twist-3 collinear factorization, and we obtain the same result both in covariant gauge and in the light-cone gauge. Moreover, we have checked the electromagnetic gauge invariance of our calculation. Our final expression for the asymmetry differs from all the previous results given in the literature. The overall sign of this asymmetry is as important as the sign of the Sivers asymmetry in Drell-Yan.