Transversity distributions and Drell-Yan spin asymmetries

TL;DR

This paper investigates transversity distributions and their impact on Drell-Yan spin asymmetries, highlighting the flavor asymmetry between antiquarks and its effects on measurable asymmetries in polarized proton-deuteron and proton-proton collisions.

Contribution

It introduces two models for antiquark flavor asymmetry and demonstrates their significant effects on Drell-Yan transverse spin asymmetries and related observables.

Findings

Both models predict a significant excess of $ar d$ over $ar u$ in transversity distributions.

The ratio $rac{ riangle_T \sigma^{pd}}{2 riangle_T \sigma^{pp}}$ effectively probes flavor asymmetry effects.

Flavor asymmetry influences the magnitude of Drell-Yan spin asymmetries.

Abstract

We discuss transversity distributions and Drell-Yan transverse double spin asymmetries. First, the antiquark flavor asymmetry $\Delta_{_T} \bar u/\Delta_{_T} \bar d$ is discussed by using two different descriptions, a meson-cloud model and a Pauli exclusion model. We find that both calculations produce a significant $\Delta_{_T} \bar d$ excess over $\Delta_{_T} \bar u$. Next, we study its effects on the transverse spin asymmetry $A_{_{TT}}$ and on the Drell-Yan proton-deuteron asymmetry $\Delta_{_T}\sigma^{pd}/2 \Delta_{_T}\sigma^{pp}$. We find that the ratio $\Delta_{_T}\sigma^{pd}/2 \Delta_{_T}\sigma^{pp}$ is very useful for investigating the flavor asymmetry effect.