The impact of initial state radiation on jets from PbPb collisions

Sammanfattning: This thesis presents the study of how initial state radiation impacts jets produced in pp and PbPb collisions, by investigating the transverse momentum spectra, the rapidity spectra and the differential jet shape. This is done for central collisions with nucleon-nucleom COM energy 2.76 TeV and 5.02 TeV. The anti-kt algorithm is used to reconstruct the jet, with the jet radii R = 0.3 and R = 1.0. Further, this thesis investigates to what extent initial state radiation can be separated from medium response on the jet. This is done by analysing events where medium response is included and events where it is not. The results show that the initial state contribution to the jet pT is quite small. It is larger for low pT-jets (100-300 GeV) and decreases rapidly for increasing pT. The initial state contribution also increases for higher rapidity, reaching quite sizeable fractions for e.g. y = 2.5. It is also shown that, for PbPb collisions, the initial state contribution is larger for jets with higher jet radius (i.e. R = 1.0) and collisions where the beam energy is higher. However, the medium response contribution will also be higher for larger jet radii and beam energy, making it hard to discern the medium response from the initial state contribution.