The Thermal Production And Diffusion Of Charm Quark In Hot/Dense QCD Matter

The heavy quark production provides an important probe for the formation and prop-erties of quark-gluon plasma(QGP)to be increated in relativistic heavy ion collision(HIC).Charm quark yield from initial hard partons scattering in the central Pb+Pb collsion can be obtained by using the Fixed-Order plus Next-to-Leading-Logarithms(FONLL)calculation in QCD combined with the Glauber model.If the temperature of medium created in HIC is high enough,the new charm quarks will be produced from the interaction between light partons in medium.These new charm quarks are the thermal production from QGP,which are also the focus of our work.The time evolution of the number of charm in central Pb+Pb collsions at LHC energy is studied by solving rate equation based 1D and 1+2D Bjorken hydodynamic model.The thermal production of charm quark in central Pb+Pb collsions also is investigated at Future Circular Colider(FCC).Since charm quark has a relatively large mass,it is difficult to thermalize in medium.We study the in-medium energy loss of charm quarks due to quasi-elastic scattering.The diffusion of charm quarks is calculated via a Langevin equation coupled to 1+2D viscous relativistic hydrodynamic model.We investigate how various paramters affect the final state spectra and elliptic flow(v2)of charm quark at LHC,such as the shadowing effect,the collective flow of the quark-gluon plasma as well as diffusion coefficient.From our numerical simulation we obtain the following results:1)Thermal charm production is sensitive to the number of charm from initial hard scatteing,the initial proper time,the temperature of medium and mass of charm.2)At(?)= 2.76 and 5.5 TeV in central Pb+Pb collisions,the contribution of thermal charm production is not obvious,while at FCC energy,its contribution can be near to 30%for initial proper time is 0.2 fm/s.3)At(?)= 2.76 TeV,the difference of thermal production based 1D and 1+2D Bjorken model is not obvious,but it does not mean the two models can be equivalent.The difference between them will significantly affect the v2 of charm quark.4)With a decrease of diffusion coefficent,the nuclear modification factor RAA and v2 of charm quarks will be increased in small transverse momentum(pt<3 GeV)region while in large pt region will be suppressed.5)Considering shadowing effect,the RAA of charm quark will weakly enhance in pt>10GeV while in 0 GeV<pt<5 GeV the RAA will be significantly suppressed.The impact of shadowing effect on v2 can be neglected.6)The collective flow effect of the medium has a great influence on v2 and RAA of charm quarks only in pt<5 GeV.