Two-gluon rapidity correlations of strong colour field in $pp$, $pA$ and $AA$ collisions

TL;DR

This paper uses the CGC formalism to analyze two-gluon rapidity correlations in different collision types, revealing ridge-like patterns in symmetric collisions and bump-like patterns in asymmetric ones, with dependencies on energy and momentum.

Contribution

It introduces a systematic calculation of two-gluon correlations in $pp$, $pA$, and $AA$ collisions using the CGC framework, highlighting the origin of ridge-like patterns.

Findings

Ridge-like correlations appear in symmetric collisions ($pp$, $AA$).

Bump-like correlations are observed in asymmetric $pA$ collisions.

Higher incident energy and lower transverse momentum enhance ridge observability.

Abstract

Using the CGC formalism, we calculate the two-gluon rapidity correlations of strong colour fields in $pp$, $pA$ and $AA$ collisions, respectively. If one trigger gluon is fixed at central rapidity, a ridge-like correlation pattern is obtained in symmetry $pp$ and $AA$ collisions, and a huge bump-like correlation pattern is presented in asymmetry $pA$ collisions. It is demonstrated that the ridge-like correlation patterns are caused by the stronger correlation with the gluon of colour source. The transverse momentum and incident energy dependence of the ridge-like correlation pattern is also systematically studied. The ridge is more likely observed at higher incident energy and lower transverse momentum of trigger gluon.