CERN Accelerating science

In relativistic heavy-ion collisions, it is expected that the quark-gluon plasma (QGP) forms at an extremely high temperature and/or high baryon density. Hard-scattered partons (quarks and gluons), resulting in sprays of particles called jets, are crucial probes to investigate the characteristics of the QGP as they strongly interact with the QGP while traversing through the medium. The energy loss of jets due to the interactions with the QGP has been experimentally observed, and the theoretical prediction of Mach shock waves induced by jets as one of the possible interactions between jets and the QGP was suggested. In this work, an analysis of the angular correlations of particles (inclusive primary hadrons and identified protons) with respect to the axes of reconstructed jets is performed, to search for possible signs of a Mach shock wave induced by jet-medium interactions. This analysis was performed with the data measured in central \PbPb collisions at \sNN = 5.02 TeV in ALICE, using the \pt range for associated particles, \ptrange{2}{4} and for background-subtracted jets above 25 \GeVc. The analysis of the jet-hadron and jet-proton correlations did not show signs of the Mach shock waves in the QGP. Additionally, hadron-hadron correlations in pseudorapidity (\deta) with the tracks belong to $\pi - \pi/4 < \Delta\phi < \pi + \pi/4$ in the jet-hadron correlations were studied in a toy Monte-Carlo simulation and in the data. The expected signals created by the Mach shock waves were observed well via the hadron-hadron correlation method in the simulation, however, the signals were not observed in the experimental data and we cannot draw a conclusion from the result due to large statistical fluctuations. This observation can imply that the actual signal might be smaller than the signal in the simulation or washed out during the QGP medium evolution. Therefore, more statistics are require for more precise measurements. Though the current statistics in the results are too limited to make a conclusive statement, it will be interesting to examine these correlation functions considering the event-plane dependence and \pt-differential results with the increased statistics, planned in future ALICE measurements in 2022.