Wei Chen, Zhong Yang, Yayun He, Weiyao Ke, Long-Gang Pang, and Xin-Nian Wang, Search for the Elusive Jet-Induced Diffusion Wake in Z/γ-Jets with 2D Jet Tomography in High-Energy Heavy-Ion Collisions, Phys. Rev. Lett. 127, 082301 (2021).
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 gives rise to a soft hadron enhancement that is uniform in the 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.
Figure: A snapshot of (a) the total and (b) jet-induced energy density distribution in the transverse plane of a semicentral PbPb collision at sNN=(5.02 TeV)2 from CoLBT-hydro simulations with a Z-jet at the spatial rapidity ηs=0 and proper time t=4.6 fm/cStraight (wavy) lines represent the transverse momenta of partons (Z boson) and dashed circles represent the two colliding nuclei.
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