Rapidity dependence of initial state geometry and momentum correlations in p+Pb collisions

TL;DR

This study investigates how initial state geometry and momentum correlations vary with rapidity in p+Pb collisions at 5.02 TeV, revealing that geometry is correlated over large rapidity ranges while momentum correlations are short-ranged, impacting interpretations of collective effects.

Contribution

It provides the first detailed analysis of rapidity dependence of initial state geometry and momentum correlations in small collision systems using the 3+1D IP-Glasma model.

Findings

Event geometry is correlated across large rapidity intervals.

Initial state momentum correlations are short-range in rapidity.

Implications for understanding collective phenomena in small systems.

Abstract

Event geometry and initial state correlations have been invoked as possible explanations of long range azimuthal correlations observed in high multiplicity p+p and p+Pb collisions. We study the rapidity dependence of initial state momentum correlations and event-by-event geometry in $\sqrt{s}=5.02~\rm{TeV}$ p+Pb collisions within the 3+1D IP-Glasma model~\cite{Schenke:2016ksl}, where the longitudinal structure is governed by JIMWLK rapidity evolution of the incoming nuclear gluon distributions. We find that the event geometry is correlated across large rapidity intervals whereas initial state momentum correlations are relatively short range in rapidity. Based on our results, we discuss implications for the relevance of both effects in explaining the origin of collective phenomena in small systems.