Elliptic And Triangular Flow Analysis In High Energy Heavy Ion Collisions At RHIC

A major goal of high energy heavy ion collisions is to determine the phase diagram of the nuclear matter, which includes to investigate the property of the matter with ex-tremely high temperature and high density produced in the collisions, to search for the possible critical point and the boundary of first-order phase transition. The top heavy ion collisions energy and the first phase of Beam Energy Scan experiment (BES-I) at RHIC cover a range of Au+Au collisions energies from √SNN=7.7 to 200 GeV. The BES-I experiment confirms the discovery of quark gluon plasma (QGP) at the top RHIC energy and narrow the boundary of critical point and first-order phase transition down to √SNN= 20 GeV. Collective flow is one of the most important hadronic observation constructed by the final state hadrons. This is because its sensitivity to the very early stage of the system evolution where QGP is dominant. In this thesis, the elliptic flow (v2) data of particles and anti-particles are fitted separately by Blast-Wave parametrization to investigate the influ-ence of radial flow to elliptic flow. Triangular flow (v3) measured by Solenoidal Tracker at RHIC (STAR) detector for inclusive charged particles and identified particles are pre-sented, further, the elliptic and triangular flow of identified particles at RHIC energies are calculated by A Multi-Phase Transport (AMPT) model.To understand the difference of elliptic flow between particles and anti-particles ob-served from BES-I by STAR collaboration, elliptic flow data in minimum bias collisions from √SNN= 7.7-2760 GeV from STAR and ALICE collaboration are fitted by Blast-Wave parametrization. The fits are performed separately for particles and anti-particles. The difference of mean transverse velocity between particles and anti-particles extracted from Blast-Wave parametrization increases with decreasing energy, which is consistent with the difference of elliptic flow between particles and anti-particles. Possible effects of feed-down, baryon stopping, antiparticle absorption, and early production times for antiparticles are discussed.Triangular flow measured by STAR detector for inclusive charged particles and i-dentified particles (π±, K±, p, p and Φ) relative to the third-harmonic event plane from 0%-80% central Au+Au collisions at ΦSNN=39 GeV and 200 GeV are presented. The pseudo-rapidity gap (ηgap=0.05,0.1 and 0.5) and energy dependence for triangular flow of inclusive charged particles are discussed. The difference of triangular flow between particles and anti-particles shows an energy dependence. The mass ordering at low pT and baryon and meson splitting at intermediate pT are observed from triangular flow of identified particles. The influence of radial flow to triangular flow and possible number-of-constituent quark scaling are discussed. It is worth to notice that the properties of triangular flow are very similar to elliptic flow but with a smaller magnitude.The major differences between elliptic and triangular flow are the different response to the initial conditions and the viscous effect of the system, therefore, better understand-ing of the initial conditions and viscous effect can be achieved by a combined analysis of elliptic and triangular flow. The elliptic flow at √SNN= 11.5,39 and 200 GeV and trian-gular flow at √SNN= 200 GeV of identified particles (π±, K±, KS0, p, p, φ, Λ and Λ) from 0%-80% central Au+Au collisions are analyzed by using AMPT model. It is shown that most of the experimental results can be reproduced with default AMPT model and string melting AMPT model with 3 mb parton scattering cross section. The differential and in-tegrated v2/v3 ratios are presented and their dependence of parton scattering cross section and particle mass are discussed. The predictions to future experiment measurement are made by AMPT model calculations.