Elliptic Flow And Elliptic Flow Fluctuations In AMPT Model

Since1983, people’s knowledge of structure of matter has made rapid progress, from the discovery of electron to the confirmation of Higgs particle at the large hadron collider(LHC) and from Rutherford’s atomic nucleus structure to the quark model then to the standard model. However, to get further research on the structure of matte, it is necessary to create high-energy conditions. Relativistic heavy ion collisions experiments create such a condition. One major purposes of which is to research the stage of nuclear matter under high temperature and high energy condition, especially may create a new stage, quark-gluon plasma, which exists in a very short time and is impossible to measure directly in experiments. So the observation of produced particles has become the primary means to research the state of new matter.A large number of experiments indicate that anisotropy flow, especially elliptic flow is the primary observation in research on relativistic heavy ion collisions. The anisotropy flow reflects the anisotropy of initial geometry in heavy ion non-central collisions. Thus, the anisotropy flow is sensitive to the early stage of collision system. This is one of reasons why the anisotropy flow has become a research subject in relativistic heavy ion collisions. The azimuth distribution asymmetry of final state particles is a primary signature of anisotropy flow. There are many methods to calculate the elliptic flow in the study including event plane method, two-particle correlation method, four-particle correlation method and Lee-Yang Zeros method. And elliptic flow fluctuations is a significant object in elliptic flow’s study. Whereas eccentricity fluctuations of initial space contribute greatly to elliptic flow.To study elliptic flow, the paper calculates and studies the centrality dependence of elliptic flow compared with the data of the STAR collaboration with event plane method, two-particle correlation method, four-particle correlation method in two different versions of AMPT model. We find that the elliptic flow value with event plane method is approximately equal to the value with two-particle correlation method.We also find that the values of elliptic flow meet the experimental data better with the parton scattering cross section of3mb in the String Melting AMPT model. This paper studies the centrality dependence of elliptic flow fluctuations relative fluctuations of elliptic flow with two-particle correlation method and four-particle correlation method. We adopt the parton scattering cross section of3mb and10mb respectively in the String Melting AMPT model. We conclude that the elliptic flow fluctuations is different in different centrality of collisions. We can see that a higher value of elliptic flow fluctuations does not necessarily mean the value of elliptic flow relative fluctuations is higher. Finally we study the initial space eccentricity including the centrality dependence of eccentricity in the reaction plane, eccentricity in the participant plane and relative fluctuations of participant eccentricity. Neglecting the contribution of nonflow, the relative fluctuations of elliptic flow should coincide with the relative fluctuations of participant eccentricity. But the result is that they have some difference in peripheral collisions.