Saturation scale fluctuations and multi-particle rapidity correlations

TL;DR

This paper investigates how fluctuations in the proton's saturation scale influence multi-particle rapidity correlations, introducing a model that explains experimental data and predicts sign changes in higher-order cumulants.

Contribution

It presents a color domain model linking saturation scale fluctuations to rapidity correlations and provides predictions for higher-order cumulants that can be experimentally tested.

Findings

Saturation scale fluctuations cause asymmetries in rapidity distributions.

The model explains the centrality dependence of two-particle correlations.

Predicted sign changes in four and eight-particle cumulants at intermediate multiplicities.

Abstract

We study the effect of intrinsic fluctuations of the proton saturation momentum scale on event-by-event rapidity distributions. Saturation scale fluctuations generate an asymmetry in the single particle rapidity distribution in each event resulting in genuine n-particle correlations having a component linear in the rapidities of the produced particles, $y_1\cdots y_n$. We introduce a color domain model that naturally explains the centrality dependence of the two-particle rapidity correlations recently measured by ATLAS while constraining the probability distribution of saturation scale fluctuations in the proton. Predictions for n = 4, 6 and 8 particle correlations find that the four and eight-particle cumulant change sign at an intermediate multiplicity, a signature which could be tested experimentally.