The Sounds of the QCD Phase Transition

TL;DR

This paper explores the generation and detection of late-stage sound waves in quark-gluon plasma during heavy ion collisions, proposing rapidity correlations as a signature of these acoustic phenomena.

Contribution

It introduces the concept of late-time sound waves from QGP cluster collapse and suggests using rapidity correlations to detect them, expanding understanding of collision dynamics.

Findings

Rapidity correlations may reveal late-time sound waves.

Widening of rapidity correlations could indicate acoustic activity.

Analytic models of distorted sound spheres are developed.

Abstract

Hydrodynamic description of a fireball produced in high energy heavy ion collisions has been recently supplemented by a very successful study of acoustic perturbation created by the initial state perturbations. We discuss sound produced at later stages of the collision, as the temperature drops below critical, $T<T_c$, and originated from the Rayleigh-type collapse of the QGP clusters. In certain analytic approximation we study distorted "sound spheres" and calculate modifications of the particle spectra and two-particle correlators induced by them. Unlike for initial state perturbations studied previously, we propose to look for those late-time sounds using rapidity correlations, rather than the azimuthal angles of the particles. We then summarize known data on rapidity correlations from RHIC and LHC, suggesting that the widening of those can be the first signature of the late-time sounds.