Research On Kernel Correction Factor Based On Boltzmann Transport Equation

The study of high energy heavy ion collisions is one of the important research directions in particle physics.Quantum-Chromodynamics is the fundamental theory to describe the strong interaction between particles.It predicts the existence of a new kind of matter at high temperature and high energy density,which is denoted as Quark Gluon Plasma(QGP),whose major degrees of freedom are the partons(quarks and gluons).QGP is expected to be produced in the ultrarelativistic heavy ion collisions.As the partons propagate through QGP,they lose energy due to gluon emission and parton splitting.Understanding the mechanism of parton energy loss is thus one of the main goals in heavy-ion collisions.The energy loss can be investigated via the study of the difference between the transverse momentum(pT)spectrum in nucleus-nucleus collisions and that in proton-proton collisions at the same collision energy.The difference is described by the nuclear modification factor(RAA).Theoretically,Fokker Planck equation,Boltzmann transport equation and Langevin equation have been utilized to describe the propagation of the energetic particles through the medium,and then to study the RAA of final particles.The method adopted in our work is to use the Boltzmann transport equation with the relaxation time approximation to investigate the RAA of identified particles as a function of pT in Pb-Pb collisions at(?)TeV and 5.02 TeV,as well as p-Pb collison at 5.02 TeV.In the model,the initial distribution is chosen as Tsallis function and the equilibrium distribution as Boltzmann-Gibbs blast wave function.In the combined fit,the following parameters are set to be in common for all particles:the non extensive parameters qpp,Tsallis temperature Tpp and equilibrium temperature Teq.The relaxation time ? is related to the interaction of the particle with the medium.Therefore,we set the ratio(tf/?)of the kinetic freeze-out time and relaxation time to be different for different particles.The model can well describe the RAA spectra of different particles to pT? 3 Ge V/c.qpp and Teq decrease with centrality nonlinearly,while tf/? increases with centrality nonlinearly.Tpp is almost independent of centrality.In addition,these trends are identical for Pb-Pb and p-Pb collisions.However,the rates of these parameters changes with centrality are different.We also disscuss the dependence of the rates on the energy and the size of the colliding system.