A Study On The Production Of Charm Hadrons In The Collision Of Pb+Pb With A Center-of-mass Energy 5.02TeV

The study of the production mechanism of charm hadrons is an important topic in high energy physics.In ultra-relativistic heavy ion collisions,charm hadron production play an important role for understanding hadronization mechanism and exploring the new properties of quark-gluon plasma(QGP).In heavy-ion collisions,most of charm quarks are produced via initial hard scatterings.Subsequently,they interact with the evolving QGP.For example,charm quark with small momentum may be thermalized by QGP and/or be boosted by the strong collective flow of QGP.Also,charm quark with large momentum may be quenched by QGP and lose its energy and momentum.Finally,charm quarks hadronize in the environment of QGP and form the charm hadrons.Recently,experiments have carried out the systematic observation on charm hadrons in pp,pA and AA collisions,and rich data are obtained.These data show a series of fascinating features for charm hadron production.Data show that Λc+/D0 exhibit significant enhancement in the intermediate transverse momentum range.Prediction of fragmentation mechanism under-estimate this ratio.Furthermore,data also show that ratio in the intermediate transverse momentum range is enhanced not only in Au+Au collisions at RHIC energies but also in pp,p+Pb and Pb+Pb collisions at LHC energies.These new features of charm hadron production attract intensive theoretical attentions.Many theoretical models are used to explain the production of charm hadrons.It is particularly worth mentioning that,the recombination mechanism plays an irreplaceable role in describing the production for charm hadrons with low and intermediate transverse momenta.In recent work of our collaboration,a quark combination model with equal velocity combination approximation is applied to the production of charm hadrons in Au+Au collisions at 200 GeV and successfully explain data of STAR collaboration.Is this model applicable in heavy-ion collision at LHC energies? Does charm hadron production exhibit any other new features?In this thesis,we apply the quark combination under EVC to production of charm hadrons in the intermediate transverse momentum range in Pb-Pb collisions at5.02 TeV,and successfully explain the ALICE data of charm hadrons and provide further theoretical predictions.The detailed contents and conclusions of this thesis are as follows:Firstly,we deduce the momentum distributions of directly produced charm hadrons in the quark combination with EVC in ultra-relativistic heavy ion collisions.Considering decay contributions from short-life resonances,we get analytical results for final state charm hadrons.Then,we apply the obtained analytical results to study charm hadron production in Pb-Pb collisions at 5.02 TeV and give numerical results of transverse momentum spectra of charmed hadrons.Finally,we present results for yield ratios such as the baryon-to-meson ratios and the nuclear modification factor.These studies show that the quark combination mechanism with EVC can successfully describe charm hadron production in Pb-Pb collisions at 5.02 TeV.