Momentum fraction and hard scale dependence of double parton scattering in heavy-ion collisions

TL;DR

This paper extends the study of double parton scattering to heavy-ion collisions, incorporating nuclear effects like shadowing and antishadowing, and proposes a model for the transverse parton distribution in nuclei.

Contribution

It introduces a model accounting for nuclear modifications to parton distributions and predicts DPS behavior in heavy-ion collisions, aiding future experimental analysis.

Findings

Reasonable agreement with $p$Pb data for effective cross section

Predictions for DPS in heavy-ion collisions at the LHC

Proposes a simple model for nuclear transverse parton distribution

Abstract

In a previous work, we studied the momentum fraction and hard--scale dependence of double parton scattering (DPS) in proton--proton collisions and the resulting dependence of the effective cross section on the final--state observables. In this paper, we extend those results to heavy--ion ($pA$ and $AA$) collisions, accounting for nuclear effects in the relevant kinematic region, namely shadowing and antishadowing. In addition to modifying the longitudinal parton distributions, these effects also alter the transverse parton distribution of the nucleus, for which we propose a simple model. We further hypothesize that partons inside a bound nucleon are more widely separated than in a free proton. We compute the effective cross section for the available $p$Pb data, obtaining reasonable agreement, and provide predictions for future measurements at the LHC. The observed dependence of our predictions on the final state indicates that DPS in heavy--ion collisions can be used to probe the transverse profile of the free proton and the bound nucleon, primarily in $pA$ collisions, as well as the transverse structure of the nucleus, mainly in $AA$ collisions.