The sound generated by a fast parton in the quark-gluon plasma is a crescendo

TL;DR

This paper models the energy deposition and resulting sound wave in quark-gluon plasma caused by a fast parton, considering both collisional and radiative energy losses, and analyzes the induced hydrodynamic response.

Contribution

It introduces a model combining collisional and radiative energy losses to study medium excitation by a fast parton in quark-gluon plasma.

Findings

Energy density waves are generated by fast partons in the plasma.

The length dependence of energy loss affects the medium's response.

The model predicts a crescendo-like sound wave in the medium.

Abstract

The total energy deposited into the medium per unit length by a fast parton traversing a quark-gluon plasma is calculated. We take the medium excitation due to collisions to be given by the well known expression for the collisional drag force. The parton's radiative energy loss contributes to the energy deposition because each radiated gluon acts as an additional source of collisional energy loss in the medium. In our model, this leads to a length dependence on the differential energy loss due to the interactions of radiated gluons with the medium. The final result, which is a sum of the primary and the secondary contributions, is then treated as the coefficient of a local hydrodynamic source term. Results are presented for energy density wave induced by two fast, back-to-back partons created in an initial hard interaction.