Production Of Meson, Baryon And Light Nuclei(A=2,3): Investigating Freeze-out Dynamics And Roles Of Energetic Quarks And Gluons In Au+Au Collisions At RHIC

In relativistic heavy-ion collisions, a high temperature matter with strong interactions is produced. The Lattice QCD calculations predict a phase transition from hadronic matter to a quark-gluon plasma state, where the quarks are believed to be deconfined. In this thesis, we report the recent STAR measurements on identified hadron and light nuclei production in Au+Au 200 GeV collisions at RHIC.Light nuclei, which have small binding energies among the constituent nucleons, are believed to be formed at the moment of the thermal freeze-out. Therefore, the production of light nuclei provides a tool to measure the freeze-out properties. Bene-fitting from the high statistic data sample taken in RHIC Run IV, we have measured the ³He((³He)|─) p_T spectra and v₂ at intermediate p_T region (2 < p_T < 6 GeV/c) and d(d) p_T spectra and v₂ at 1 < p_T < 4 GeV/c. The coalescence parameters B₂ and B₃ are extracted. The low p_T (0.2 < p_T < 1 GeV/c) d|- v₂ has also been measured. We find that B₂ has the similar value with (B₃)^1/2. It indicates the d(d|-) and ³He((³He)|─) have a similar freeze-out time. We compare the B₂ and (B₃)^1/2 to the pion freeze-out volume measured by HBT study. It is found that the B₂ and (B₃)^1/2 are proportional to the pion freeze-out volume in various centrality collisions. The freeze-out volume is found to be constant with (s_NN)^1/2 at (s_NN)^1/2 > 20 GeV when we compare our results to the low energy results. The d + d|- v₂ is found to follow the atomic mass number (A) scaling within errors and we observe a deviation of ³He + (³He)|─v₂ from the A scaling. The first negative v₂ at RHIC has been observed for low p_T d|- in mid-central collisions. This is consistent with a large radial flow scenario. We have systematically studied the anti-baryon phase space density inferred from d|-/p|- measurements in various collision systems at various energies. It is found that the anti-baryon density at the final-state coalescence saturates when the process from different collisions involving gluons.We use the particle identification capability of the STAR TPC and TOF detectors to measure theÏ€^±and p(p|-) spectra in large transverse momentum range (0.3 < p_T < 12 GeV/c). The relative baryon enhancement is observed in central collision and this can be explain by the partonic coalescence phenomena. At high p_T, the suppressions of meson and baryon are observed to be the same, which are not consistent with the partonic energy loss calculation of pQCD. This points to possible phenomena beyond pQCD energy loss in a strong interacting matter.