Sivers asymmetry of Drell-Yan production in small-$x$ regime

TL;DR

This paper investigates the Sivers asymmetry in Drell-Yan production at small-$x$, demonstrating consistency across different factorization approaches and proposing it as a probe for spin physics and saturation effects.

Contribution

It provides a unified analysis of Sivers asymmetry in the small-$x$ regime and explores its potential as a probe for transverse spin and saturation phenomena.

Findings

Sivers asymmetry aligns with both TMD and collinear formalisms in the small-$x$ regime

Estimates of asymmetry for polarized p+p and p+A collisions

Drell-Yan production as a probe for spin and saturation effects

Abstract

We study the Sivers single spin asymmetry of the Drell-Yan lepton pair production in the small-$x$ regime. We find that in the corresponding kinematic region the spin asymmetry calculated in the small-$x$ approach is consistent with either the usual transverse-momentum-dependent factorization formalism or the collinear factorization formalism, respectively. We estimate the Sivers asymmetry for both polarized p+p and p+A collisions and argue that the Drell-Yan production is an interesting and unique probe for both the transverse spin physics and the small-$x$ saturation effect.