Heavy Quark Dynamics In Quark-Gluon Plasma

Many experimental evidences at the Relativistic Heavy-Ion Collider(RHIC)and the Large Hadron Collider(LHC)have confirmed the existence of quark-gluon plasma(QGP),such as the strong anisotropic flow of the final state particles at low transverse momentum(pT)and the suppression of hadrons at high pT;the latter phenomenon is called jet quenching.Heavy quarks serve as excellent probes of the QGP matter as they are primarily produced from the early-state hard scatterings and can encode the information of the entire evolution history of the QGP fireballs.In this dissertation,we utilize heavy and light flavor hadrons’ RAA at high pT to probe the flavor and mass dependences of parton energy loss and jet quenching,and use heavy flavor hadrons RAA and v2 at low and intermediate pT to investigate perturbative and non-perturbative interactions between heavy quarks and QGP medium.Relativistic heavy-ion experiments have observed similar quenching effects for(prompt)D mesons compared to charged hadrons for transverse momenta larger than 6-8 GeV,which remains a mystery since heavy quarks typically lose less energies than light quarks and gluons.Within a next-to-leading-order(NLO)perturbative QCD(pQCD)framework which allows to account for both quark and gluon contributions to light and heavy flavor hadron productions,we calculate the transverse momentum spectra for light charged hadrons,heavy D mesons and B mesons at high pT in protonproton collisions.By combining the NLO-pQCD framework with the linear Boltzmann transport(LBT)model and a(3+1)-dimensional hydrodynamic model CLVisc,we obtain,for the first time,a satisfactory description of the experimental data on the nuclear modification factors for charged hadrons,D mesons,B mesons and B-decayed D mesons simultaneously over a wide range of transverse momenta(8-300 GeV).This presents a solid solution to the flavor puzzle of jet quenching.Our study also demonstrates that perturbative QCD calculation is sufficient for studying the color,mass and energy dependence of parton energy loss and jet quenching.The perturbative interactions between heavy quarks and QGP fail to describe heavy mesons RAA and v2 at low and intermediate pT.To address this issue,we extend the linear Boltzmann transport model by implementing a generalized Cornell-type potential that incorporates both short-range Yukawa interaction and long-range color confining interaction between heavy quarks and the QGP medium.Combining our new approach for heavy-quark-QGP interaction with a(3+1)-dimensional hydrodynamic model CLVisc and a hybrid fragmentation-coalescence model,we obtain a satisfactory description of heavy meson RAA and v2 from low to intermediate to high pT observed at both RHIC and the LHC.By the model-to-data comparison,we extract for the first time the in-medium heavy quark potential from open heavy flavor measurements;the result is in good agreement with the lattice QCD calculation.Our study indicates that while jet quenching at high pT is dominated by perturbative QCD interactions,non-perturbative interactions are indispensible for understanding heavy flavor quenching and flow at low and intermediate pT.Many experimental and theoretical studies have shown that the mini-QGP may be produced in p-Pb collisions.However,no jet quenching has been observed(RpPb～1).In order to understand this puzzle,we utilize relativistic Langevin transport model and the linear Boltzmann transport model to explore the system size dependence of heavy and light flavor hadrons suppression and elliptic flow in Pb-Pb,Xe-Xe,Ar-Ar,and O-O collisions.We find that the suppression of heavy and light hadrons mainly relies on the system size,while their elliptic flow coefficients rely on both the system size and the geometric anisotropy of the QGP.Sizable suppression and flow are predicted for both D and B mesons in O-O collisions,which serves as a crucial bridge of jet quenching between large and small collision systems.Our results indicates that RpA～1 in proton-nucleus collisions is mainly due to the small size of the produced nuclear medium.Scaling behaviors between different collision systems are shown for heavy meson suppression factor and the bulk-eccentricity-rescaled elliptic flow as functions of<Npart>in heavy-ion collisions.