Search for the elusive jet-induced diffusion wake in $Z/\gamma$-jets with 2D jet tomography in high-energy heavy-ion collisions

TL;DR

This paper investigates the elusive jet-induced diffusion wake in high-energy heavy-ion collisions, using advanced modeling and jet tomography to identify the diffusion wake signal amidst medium modifications and initial interactions.

Contribution

It introduces a combined Boltzmann transport and hydro model to distinguish diffusion wake effects and employs gradient jet tomography to localize jet origins in $Z/ extgamma$-jet events.

Findings

Medium modification from initial MPI causes uniform soft hadron enhancement.

Jet response and gluon radiation dominate enhancement in jet direction.

Diffusion wake becomes observable after subtracting MPI contributions.

Abstract

Diffusion wake is an unambiguous part of the jet-induced medium response in high-energy heavy-ion collisions that leads to a depletion of soft hadrons in the opposite direction of the jet propagation. New experimental data on $Z$-hadron correlation in Pb+Pb collisions at the Large Hadron Collider show, however, an enhancement of soft hadrons in the direction of both the $Z$ and the jet. Using a coupled linear Boltzmann transport and hydro model, we demonstrate that medium modification of partons from the initial multiple parton interaction (MPI) gives rise to a soft hadron enhancement that is uniform in azimuthal angle while jet-induced medium response and soft gluon radiation dominate the enhancement in the jet direction. After subtraction of the contributions from MPI with a mixed-event procedure, the diffusion wake becomes visible in the near-side $Z$-hadron correlation. We further employ the longitudinal and transverse gradient jet tomography for the first time to localize the initial jet production positions in $Z/\gamma$-jet events in which the effect of the diffusion wake is apparent in $Z/\gamma$-hadron correlation even without the subtraction of MPI.