Performance of jet subtraction in pPb and PbPb collisions, without collectivity

University essay from Lunds universitet/Teoretisk partikelfysik; Lunds universitet/Institutionen för astronomi och teoretisk fysik

Abstract: We investigated the performance of basic jet subtraction, by the utilization of jet reconstruction generally used at the Large Hadron Collider (LHC). This was done by studying Z-bosons, in the dielectron decay channel, and the associated jet correlation in pp, pPb and PbPb collisions, using datasets generated by the Monte Carlo generator PYTHIA8. The PbPb collisions at $\sqrt{s_{NN}} = 2.76$ TeV and pPb collisions at $\sqrt{s_{NN}} = 5.012$ TeV were generated with the full simulated heavy-ion background by using the Angantyr model (PYTHIA), and compared to the results of pp collisions with a corresponding collision energy. The way the Angantyr model works is by essentially stacking individual nucleon-nucleon sub-collisions on top of each other and hadronize them together, allowing us to study only the microscopic interactions without any assumptions of a thermalized medium or collective interaction. The measurements of Z+leading-jet from these collisions are presented as a function of the transverse momentum balance between Z$^0$ and the jet, the azimuthal angular and the pseudorapidity separation between the Z$^0$ and the jet, and the jet profile. These measurements are presented as a function of collision centrality. The results of the investigation suggests that the jet subtraction performs considerably well correcting the transverse momenta of the jet for peripheral PbPb collisions and pPb events, but the shape of the jets remain strongly damped in the underlying event of central PbPb collisions.

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