Sound Waves from Quenched Jets

TL;DR

This paper uses hydrodynamics to analyze sound waves generated by quenched jets in heavy ion collisions, revealing how these waves distort particle spectra and freezeout surfaces, with implications for interpreting experimental data.

Contribution

It introduces a hydrodynamic model of sound propagation from quenched jets, including the effects of radial flow and wave distortion on observable particle spectra.

Findings

Conical Mach waves are significantly distorted by radial flow.

Particle spectra are mainly influenced by the intersection of waves with freezeout surfaces.

Predictions suggest dijet studies at LHC can test the model more effectively.

Abstract

Heavy ion collisions at RHIC/LHC energies are well described by the (nearly ideal) hydrodynamics. Last year this success has been extended to higher angular harmonics, $v_n,n=3..9$ induced by initial-state perturbations, in analogy to cosmic microwave background fluctuations. Here we use hydrodynamics to study sound propagation emitted by quenched jets. We use the so called "geometric acoustics" to follow the sound propagation, on top of the expanding fireball. The conical waves, known as "Mach cones", turn out to be strongly distorted. We show that large radial flow makes the observed particle spectra to be determined mostlly by the vicinity of their intersection with the fireball's space-like and time-like freezeout surfaces. We further show how the waves modify the freezeout surfaces and spectra. We end up comparing our calculations to the two-particle correlation functions at RHIC, while emphasizing that studies of dijet events observed at LHC should provide much better test of our theory.