Universality of the Diffusion Wake from Stopped and Punch-Through Jets in Heavy-Ion Collisions

TL;DR

This study demonstrates that the diffusion wake created by jets in heavy-ion collisions is a universal feature, largely unaffected by whether jets punch through or stop inside the medium, impacting observed angular correlations.

Contribution

It shows the universality of the diffusion wake in hydrodynamic models, regardless of jet stopping or punching through, using (3+1)-D ideal hydrodynamics with source terms.

Findings

Diffusion wake is largely insensitive to jet stopping or punching through.

The diffusion wake dominates over Mach cone signals after freeze-out.

The result is independent of the direction of momentum deposition.

Abstract

We solve (3+1)-dimensional ideal hydrodynamical equations with source terms that describe punch-through and fully stopped jets in order to compare their final away-side angular correlations in a static medium. For fully stopped jets, the backreaction of the medium is described by a simple Bethe-Bloch-like model which leads to an explosive burst of energy and momentum (Bragg peak) close to the end of the jet's evolution through the medium. Surprisingly enough, we find that the medium's response and the corresponding away-side angular correlations are largely insensitive to whether the jet punches through or stops inside the medium. This result is also independent of whether momentum deposition is longitudinal (as generally occurs in pQCD energy loss models) or transverse (as the Bethe-Bloch formula implies). The existence of the diffusion wake is therefore shown to be universal to all scenarios where momentum as well as energy is deposited into the medium, which can readily be understood in ideal hydrodynamics through vorticity conservation. The particle yield coming from the strong forward moving diffusion wake that is formed in the wake of both punch-through and stopped jets largely overwhelms their weak Mach cone signal after freeze-out.