Evidence of the medium response to hard probes with Z-hadron correlations in PbPb and pp collisions

December 17 2024 (in-person)
Chen, Yi (Luna) (Vanderbilt University)
Host: Peter Jacobs
Title: Evidence of the medium response to hard probes with Z-hadron correlations in PbPb and pp collisions
Abstract: In ultrarelativistic heavy-ion collisions at RHIC and LHC, a new state of matter known as the quark-gluon plasma (QGP) is believed to be created. As high-energy quarks or gluons traverse the plasma, their interactions with the QGP reduce their energy while simultaneously injecting energy into the QGP, which then propagates. This interaction and energy propagation result in intriguing phenomena, including the diffusion wake, observed in several phenomenological models.
In this seminar, I will present a recent measurement from the CMS collaboration that successfully isolates some of these wake effects for the first time. The measurement analyzes the charged hadron distribution in azimuthal angle and pseudorapidity associated with a Z boson in PbPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV with the CMS experiment. A stronger modification of charged hadron distributions near the Z boson is observed in PbPb collisions compared to the pp reference. This result provides new insights into the interactions within the QGP and contributes to a deeper understanding of the jet quenching phenomenon.