Production Of (Anti-)Nuclei And Hypernuclei In Nucleus-Nucleus Collisions At RHIC And LHC Energies

The Big Bang theory holds that matter and antimatter are formed with comparable abundance in the initial stage of the Universe,while reaching a stage with only visible amounts of matter being present.It remains a continuous mystery of modern natural science how this symmetry got lost in the evolution of the Universe.According to Quantum Chromodynamics（QCD）,high-energy nucleus-nucleus collisions create a new state of matter,Quark-Gluon Plasma（QGP）,formed by a large number of free quarks and gluons,which is similar to that of the Universe microseconds after the Big Bang.However,the relatively short-lived expansion of the QGP state can avoid annihilation between matter and antimatter.Thus,these high-energy collisions can provide an efficient means of producing and studying antimatter.In recent years,the experimental and theoretical studies on the production of（anti-）nuclei and（anti-）hyper-nuclei as well as the properties of the QGP state have been hot topics in the frontier of high-energy nuclear physics,due to the discovery and measurement of light anti-nuclei and the QGP state.Light（anti-）nuclei and（anti-）hypernuclei,including deuteron（d）,triton（3H）,helium-3（³He）,hypertriton（_Λ³H）and their anti-partners,are taken as the research objects in the thesis.And the microscopic framework of“a transport model plus a coalescence model" is built,that is,the parton and hadron cascade（PACIAE）model and the dynamically constrained phase-space coalescence（DCPC）model,which is then applied to describe the production of（anti-）nuclei and（anti-）hypernuclei and to study several properties of the QGP state.The research contents can be divided into the following four parts:Firstly,the Chiral Magnetic Effect（CME）may survive from the expansion of the quark-gluon plasma fireball and charge separation effect is an important consequence of the CME.In terms of available experimental data and theory analysis,the semi-empirical physics function of the CME-induced initial charge separation mechanism for PACIAE model is induced for various symmetric nucleus-nucleus collisions.Then the new upgraded issue of PACIAE 2.2.1 is obtained with the above mechanism.Furthermore,the charge correlation parameter γ and the multiplicity distribution of final-state particles,which are considered to be related to the CME physics,are separately calculated in Au+Au collisions at RHIC and Pb+Pb collision at LHC.The simulated results are consistent with the experimental data,which means that high-energy nucleus-nucleus collisions can be better described by the new PACIAE 2.2.1 model with the CME mechanism.Secondly,the isobaric ₄₄⁹⁶Ru+₄₄⁹⁶Ru and ₄₀⁹⁶Zr+₄₀⁹⁶Zr collisions at RHIC are the best experimental method to identify and study the CME.The production of three-body（anti-）nuclei（_Λ³H（_Λ³H）,³H（³H）,and ³He（³He））is computed by the PACIAE 2.2.1+DCPC model in ₄₄⁹⁶Ru+₄₄⁹⁶Ru and ₄₀⁹⁶Zr+₄₀⁹⁶Zr collisions.One can find that the production of anti-nuclei is less than their corresponding nuclei,meaning that the abundance asymmetry of matter and antimatter exists;and（anti-）hypernuclei are difficult to produce than（anti-）nuclei with the same number of nucleons.Besides,the coalescence parameters B_A and the strangeness population factor s₃ of（anti-）nuclei and（anti-）hypertriton are also calculated,and the results are consistent with the experimental data of Cu+Cu,Au+Au,and Pb+Pb collisions from RHIC and LHC.In addition,comparing with the calculated results in these two collisions,the production of（anti-）hypertriton and（anti-）nuclei is found to be affected by the CME to a certain extent.Thirdly,the investigation of QCD phase transition and the search for QCD critical endpoint are the hot issues in particle physics.The nuclear system size scan program from ¹⁰B+¹⁰B to ²³⁸U+²³⁸U collisions at RHIC is proposed,then（anti-）nuclei and（anti-）hypernuclei are produced to search for the possible signals of QCD critical endpoint.Specifically,the PACIAE+DCPC model is used to produce the production of（anti-）nuclei and（anti-）hypernuclei in ten collision systems,including ¹⁰B+¹⁰B,¹²C+¹²C,¹⁶O+¹⁶O,²⁰Ne+²⁰Ne,²⁷Al+²⁷Al,⁴⁰Ar+⁴⁰Ar,⁶³Cu+⁶³Cu,_<sup>96Ru+_<sup>96Ru,¹⁹⁷Au+¹⁹⁷Au and ²³⁸U+²³⁸U collisions.Then the yield ratios of deuteron to proton（d/p）,helium-3 to proton（³He/p）,and hypertriton to hyperon（_Λ³H/Λ）,as well as the double yield ratios Opdt and the strangeness population factor s₃ are discussed.One can see that a common suppression behavior for the yield ratios of d/p,³He/p,and ³H/A exists in the relatively small collision system,and the much stronger suppression of yield ratios for ΛH/Λ than d/p and ³He/p is presented;Especially it is also interesting to see the strangeness population factor s₃ shows an obvious ’turning point’ in the region of atomic mass number A around 12 to 27.Extensive research shows that the suppression and‘turning point’ phenomena may be mainly explained by the size effect of the produced nuclei and the emission source of different collisions.Besides,whether it is related to the QCD critical endpoint remains to be further studied.In addition,the model calculations are in agreement with statistical-thermal models and the available experimental data for Au+Au collisions at RHIC-STAR and Pb+Pb collisions at LHC-ALICE within uncertainties.Finally,the nuclear modification factor RAA is an important means of evaluating the jet quenching effect in the QGP.The transverse momentum distributions of（anti-）meson,（anti-）baryon,and（anti-）deuteron are simulated by PACIAE+DCPC model in pp and Pb+Pb collisions at LHC energy,then their nuclear modification factor RAA distributions in Pb+Pb are obtained.The calculated results show that the RAA distribution of（anti-）nuclei d（d）is similar to that of（anti-）mesons π⁺（π^-）and（anti-）baryons p（?）,and the R_AA suppression of（anti-）nuclei is more significant than that of（anti-）hadrons;The RAA of antiparticles is the same as that of particles;Besides,the suppression of RAA at high-pT strongly depends on event centrality and mass of the particles.In addition,the transverse momentum distributions of the double nuclear modification factors R_AA^D and the coalescence parameters B_A are also computed.In particular,the simulation results further validate that QGP state has been formed in Pb+Pb collisions at LHC.