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/γ-jet events in which the effect of the diffusion wake is apparent in Z/γ-hadron correlation even without the subtraction of the MPI contribution.
Highlights
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
We further employ the longitudinal and transverse gradient jet tomography for the first time to localize the initial jet production positions in Z=γ-jet events in which the effect of the diffusion wake is apparent in Z=γ-hadron correlation even without the subtraction of the MPI contribution
We will show that medium modification of MPI partons leads to an enhanced soft Z=γ-hadron correlation which is uniform in the azimuthal angle and offsets the effect of the diffusion wake
Summary
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. We further employ the longitudinal and transverse gradient jet tomography for the first time to localize the initial jet production positions in Z=γ-jet events in which the effect of the diffusion wake is apparent in Z=γ-hadron correlation even without the subtraction of the MPI contribution.
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