Investigating the excitation function of HBT radii for L\'evy-stable sources

TL;DR

This paper examines how using a Lévystable source model instead of a Gaussian affects the interpretation of HBT radii excitation functions in heavy-ion collisions, which are crucial for locating the QCD critical point.

Contribution

It demonstrates that the source shape assumption significantly influences the observed excitation function behavior of HBT radii in femtoscopy analyses.

Findings

Lévy-stable source description alters the excitation function interpretation.

Source size is strongly linked to source shape and power-law behavior.

Proper modeling changes the perceived non-monotonic signals.

Abstract

Contemporary heavy-ion physics research aims to explore the phase diagram of strongly interacting matter and search for signs of the possible critical endpoint on the QCD phase diagram. Femtoscopy is among the important tools used for this endeavor; there have been indications that combinations of femtoscopic radii parameters (referred to as HBT radii for identical boson pairs) can be related to the system's emission duration. An apparent non-monotonic behavior in their excitation function thus might signal the location of the critical point. In this paper, we show that conclusions drawn from the results obtained with a Gaussian approximation for the pion source shape might be altered if one utilizes a more general L\'evy-stable source description. We find that the characteristic size of the pion source function is strongly connected to the shape of the source and its possible power-law behavior. Taking this into account properly changes the observed behavior of the excitation function.