The Shape of the Correlation Function

TL;DR

This paper investigates the non-Gaussian shape of the correlation function in ultrarelativistic nuclear collisions, focusing on how various effects influence its form and the applicability of Lévystable distributions.

Contribution

It demonstrates how non-critical effects can significantly alter the Lévystable parametrization of the correlation function shape.

Findings

Lévy index can deviate from 2 due to resonance decays and fluctuations

First-order Lévy expansion provides correction insights

Correlation function shape is sensitive to non-critical effects

Abstract

The correlation function measured in ultrarelativistic nuclear collisions is strongly non-Gaussian. Using two different models we study which effects can influence its shape and how much. In particular, we focus on the parametrizations expressed with the help of L\'evy-stable distributions. We show that the L\'evy index may deviate substantially from 2 due to non-critical effects such as resonance decays, event-by-event fluctuations and functional dependence on $Q_{LI}$ or similar. We also study the corrections including the first-order L\'evy expansion.