Nuclear Modification Of D Mesons In AuAu And CuCu Collisions At 200AGeV At Relativistic Heavy-Ion Collider

Relativistic heavy ion collisions can create the extremely hot and dense quark-gluon plasma(QGP),which has existed in early stage of the universe.We can study the properties of QGP using "hard probes" and "soft probes",which should be helpful for our understanding of the evolution of the early universe."Hard probes" mean the high energy particles which are produced at the very early stage of heavy-ion collisions via hard scattering.Therefore we can calculate their production cross section using perturbative QCD.Since their formation time is shorter than the production time of QGP,so they can propagate through and observe the whole evolution history of the QGP matter.Therefore "hard probes"can be a valuable tool to probe the properties of QGP.Heavy quark(c quark and b quark)is an important type of "hard probes",they have the large masses:Mc?1.5GeV,Mb ? 4.7GeV.In this thesis,I study the the energy loss of heavy quark(c quark)using a Linear Boltzmann Transport model include both elastic scatterings and inelastic scatterings.For the process of 2 ? 2 elastic scatterings,we can calculate the scattering cross section and collision rate by using perturbation QCD.The gluon radiation spectrum is adopted from the high-twist calculation for parton energy loss from medium-induced radiation process.We study the elastic energy loss of 20 GeV?40 GeV charm quark in a static medium with 300 MeV temperature as a function of time.We find that the energy loss suffered by the heavy quark from elastic scattering and induced gluon radiation are comparable at the early stage,but the energy loss of heavy quark caused by the gluon radiation dominate at the later times.Heavy quarks will hadronize into their hadronic bound states,after they pass through QGP.We use a hybrid fragmentation plus recombination model to simulate the hadronization process of heavy quarks at all momentum scales.We calculate the pT distribution of D mesons produced from heavy quarks,and the nuclear modifi-cation factor RAA for 200A GeV Au-Au and 200A GeV Cu-Cu collisions for different centralities.We find that the nuclear modification factor RAA of AuAu is less than CuCu for same centrality,since the system size of AuAu is bigger than CuCu for same centrality.We further calculate the nuclear modification factor RAA for AuAu and CuCu collisions as a function of the centrality and<Npart>,from which we can find that the nuclear modification factor RAA for the same collision energy only depends on the system size.