Universality in nuclear dependence coefficient $\alpha(q_T)$

TL;DR

This paper derives a universal functional form for the nuclear dependence coefficient in particle production processes, showing it is independent of atomic number and determined by measurable quantities, aligning with experimental data.

Contribution

It introduces a universal quadratic form for $oldsymbol{ ext{alpha}(q_T)}$ applicable to Drell-Yan and J/psi production, with parameters linked to measurable or calculable factors.

Findings

$oldsymbol{ ext{alpha}(q_T)}$ follows a universal quadratic form at small $q_T$

Parameters $a$ and $b$ are determined by measurable quantities

The form is consistent with existing experimental data

Abstract

We derive the nuclear dependence coefficient $\alpha(q_T)$ for Drell-Yan and J/$\psi$ production. We show that at small $q_T$, the $\alpha(q_T)$ is given by an universal functional form: $\alpha(q_T)=a+b q_T^2$, and the parameters $a$ and $b$ are completely determined by either perturbatively calculable or independently measurable quantities. This universal functional form $\alpha(q_T)$ is insensitive to the $A$, and is consistent with existing data.