Longitudinal fluctuations of the fireball density in heavy-ion collisions

TL;DR

This paper investigates how longitudinal shape fluctuations of the fireball in heavy-ion collisions create complex rapidity correlations, offering a method to analyze initial conditions in such collisions.

Contribution

It demonstrates that longitudinal fluctuations produce rapidity correlations depending on both rapidity difference and sum, providing a new way to study initial fireball conditions.

Findings

Fluctuations generate correlations depending on y1 + y2 and y1 - y2.

Method to extract fluctuation components from two-particle correlations.

Potential to study initial conditions in heavy-ion and proton-proton collisions.

Abstract

We show that fluctuations of the fireball shape in the longitudinal direction generate nontrivial rapidity correlations that depend not only on the rapidity difference, y_{1} - y_{2}, but also on the rapidity sum, y_{1} + y_{2}. This is explicitly demonstrated in a simple wounded nucleon model, and the general case is also discussed. We show how to extract different components of the fluctuating fireball shape from the measured two-particle rapidity correlation function. The experimental possibility of studying the longitudinal initial conditions in heavy-ion and proton-proton collisions is emphasized.