Saturation scale fluctuations and multi-particle rapidity correlations

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.