A background-free signal of jet-induced diffusion wake in quark-gluon plasma

TL;DR

This paper introduces a background-free rapidity asymmetry observable to detect jet-induced diffusion wake in quark-gluon plasma, demonstrated through simulations of dijets and gamma-jets in heavy-ion collisions.

Contribution

It generalizes the rapidity asymmetry measurement to various jet configurations and proposes a new background-canceling method for more accurate detection.

Findings

Background-free rapidity asymmetry observed in simulations.

Asymmetry weakens with increasing hadron pT.

Baseline subtraction has negligible effect.

Abstract

Rapidity asymmetry of jet-hadron correlation has been proposed as a robust signal of dijet-induced diffusion wake in quark-gluon plasma in high-energy heavy-ion collisions. We generalize this observable to other jet configurations such as {\gamma}/Z0-jets and propose a new method to compute the rapidity asymmetry that is free of background. In this new method, the rapidity of the trigger is fixed or restricted to a symmetrical range while the rapidity of the associated jet is varied. The rapidity asymmetry is defined as the difference between the hadron rapidity distribution in the opposite azimuthal direction of the jet (or the same direction of the trigger) with different associated jet rapidities. Since the background in this hadron rapidity distribution with different associated jet rapidity is identical, it will be completely canceled in the rapidity asymmetry. Such background-free rapidity asymmetry caused by jet-induced diffusion wake is demonstrated in CoLBT-hydro simulations of dijets and {\gamma}-jets in Pb+Pb collisions at the LHC, which weakens as hadron pT increases, and subtraction of a p+p baseline has a negligible effect.