Resummation Improved PQCD Approach On Jet Transport Coefficient

The properties of the famous quark-gluon plasma (QGP) .created in relativis-tic heavy-ion collisions, relating to the state of the early universe, can be studied by techniques of jet tomography, which is the study of the modification that this hot and dense medium has on hard partonic jets that are produced in such violent collisions.This modification known as the jet quenching phenomena, is responsible in describ-ing the jet-medium interaction via medium induced gluon radiation that results in transverse momentum broadening and energy loss effect of the final state jet. In this study, we have investigated these two effects in detail, which can be reflected on the azimuthal angular distribution and the momentum asymmetry ratio distribution of the dijet, dihadron and hadron-jet de-correlations.We first establish a pp baseline calculation for the angular correlation by em-ploying the Sudakov resummation formalism that takes into account the vacuum soft gluon radiations, which is crucial and necessary in order to understand the al-ternating diverging behaviour in the traditional perturbative QCD calculations. By implementing the medium induced broadening effect (p12), we demonstrated that the so-called jet quenching parameter q can be extracted from the angular de-correlations observed in AA collisions. A global x2 analysis of dihadron and hadron-jet angular correlation data renders the bets fit of (p12) ～ 13 GeV2 for a quark jet at RHIC peak energy using the CERN MINUIT package along with hydrodynamic code simulating the space-time evolution of the medium.We then examine the dijet asymmetry ratio distribution and found an interesting bound of xJ≥1/n-1 for any 2 → n process given that the total transverse momentum of the system is conserved. Since all previous studies have focused on comparing theoretical calculations with the folded, uncorrected experimental data, we have thus developed the first systematic analytical approach in calculating the dijet asymmetry ratio pp baseline by utilizing both perturbative QCD and Sudakov resummation for-malism. We found that both formalisms are vital in describing the different domains of the phase space, and therefore the resummation improved pQCD approach have obtained good agreement with the most up-to-date fully corrected ATLAS pp data.Combining with the BDMPS jet energy loss formalism, we then extracted the value of the jet transport coefficient q0 ～2-6 GeV2/fm for the quark-gluon plasma created in PbPb collisions at 2.76A TeV.Both work have presented a new and more direct method in probing the proper-ties of the strongly-coupled QCD medium, and pave the way for a more complete and deeper understanding of the QGP. Further experimental and theoretical efforts along the direction of these work shall significantly advance the quantitative understand-ing of the transverse momentum broadening and dijet asymmetry mechanism, which can then help us acquire unprecedented knowledge of the jet quenching parameter in relativistic heavy-ion collisions.