The Bin-bin Multiplicity Correlation Of Phase Space In Hadron-hadron And Relativistic Heavy Ion Collisions

Exploring the origin of matter and their microscopic structure is one of foreland fields of modern physics. It is generally considered today that quark and gluon are the component unit of matter. Quantum chromodynamics (QCD) is very successful to describe strong interaction between quark and gluon. The QCD theory has two basic properties. one is "asymptotic freedom". When quarks get very close, the coupling constant becomes extremely small. The other is "confined quark", that means quarks are confined in hadrons and there is no free quark. The mystery of quark confinement was thought as a great puzzle of the 20th century. In the 1970s, T.D.Lee et al. proposed that a new formed matter- Quark Gluon Plasma (QGP) would be produced in a environment with enough high density and high temperature, according the relativistic heavy ion collisions. This leads to the rapid development of cixperimental and theoretical study on relativistic heavy ion collision.In the beginning of the century, the relativistic heavy ion collider (RHIC) was build and run in the Brookheaven National Laboratory in U.S. with colliding energy up to 200GeV/nucleon. Through several years of hard research, we observe parton (quark or gluon) degree of freedom and believe the new formed matter QGP has been formed. There are three major evidence:1)The energy density of initial state is nearly a hundred times greater than that of nuclear matter; 2)There are a large quantity of energy loss when particles at high pt go through the hot and dense matter; 3)The anisotropic collective behavior of particles has been observed and the elliptic flow of particles at medium pt has a property of quark scaling, all of which can be well described by ideal hydrodynamics. Combining these experimental results, we believe that the strongly coupled quark and gluon plasma has been formed(sQGP).However, the ideal hydrodynamics model has some limitations on the description of elliptic flow. It can only describe the elliptic flow of particles at low pt region, but fail for that of high pt. It can't fit the elliptic flow parameter of different particles, especially the heavy flavor particles. What's more, for (?) GeV CuCu collision, the experimen-tal result of elliptic flow is much larger than the calculation of ideal hydrodynamics. Soon, U.heinz et al. applied the viscous hydrodynamics into the relativistic heavy ion collisions and prove it could well reproduce the experimental data through changing the viscosity parameter. All of these show the new formed matter is not ideal fluid, but viscous fluid. How to measure the viscosity of QGP becomes another key problem.The neighboring azimuthal bin correlation pattern is suggested to measure the shear viscosity of the new matter. In ideal fluid, there is no internal interaction and the flow layer has the same viscosity. While in viscous fluid, internal interaction exists between layers and there is viscosity gradient. The new physicst measure can describe the interaction between fluid layers and reflect the internal information of collective flow. We derive the formula of shear viscosity by combing the dissipation energy theory in viscous hydrodynamics and the azimuthal correlation pattern. When the physics information of final particles is known, we can obtain the shear viscosity of new formed matter. In this view, the new method of measuring shear viscosity has a strong feasibility and can help us learn more about the new formed matter in current RHIC experiment.A multi-phase transport model (AMPT) includes both hadron-level and parton-level interaction, which is a success to describe relativistic heavy ion collision. Based on this model, we explore the shear viscosity of dense matter produced in (?) GeV AuAu collision. We present the azimuthal angle dependence of neighboring bin correlation pat-tern and the average transverse velocity. The thermal model are used to fit the average transverse velocity of final particles. As a comparison, we study the case of cross sectionσ= 3mb andσ=10mb. It is found that the larger cross section is, the smaller the shear viscosity is, which is consistent with the calculation of microscopic theory.In this paper, rapidity correlation pattern is also applied to relativistic heavy ion collision. Two correlation patterns-neighboring bin and fixed-to arbitrary rapidity correlation pattern are suggested. Different from the traditional physics measure of cor-relation, they can simultaneously record the change of correlation strength with spatial position of bin and the distance between bins. They can help us an excellent study of the short and long range correlation (LRC) in rapidity direction. In the market, forward-backward correlation from STAR experiment have inferred that the long range rapidity correlation pattern origins from the Color Glass Condensate (CGC) of initial state. How-ever, some research show that the fluctuation of multiplicity and short range correlation can also give rise to LRC. Is LRC a result of fluctuation or CGC?We present the centrality dependence of rapidity correlation pattern for(?) GeV AuAu collision in the AMPT with string-melting. With the centrality increasing, it is observed that the value of correlation pattern decreases and the corresponding long range correlation is greatly weakened. This is not consistent with experimental data from This may indirectly prove the long range correlation is mainly from the effect of Color Glass Condensate. Moreover, in the samples for fixed impact parameter, we further study the rapidity gap dependence of correlation pattern and forward-backward correlation. It provides a way to eliminate or decrease at least the effect of fluctuation for LRC.In non-central collision, elliptic flow is a key observable in the relativistic heavy ion collision, which can reflect the physics information of initial state. We study the multiplic-ity dependence of elliptic flow for Au+Au collisions at (?) GeV by AMPT with string melting. It is first shown that for at fixed impact factor b, elliptic flow varies with multiplicity monotonously but is not a simple fluctuation. After scaling elliptic flow by initial eccentricity of the nuclear overlap area, we obtain that it increases with centrality and then becomes a constant, which is indicated that the system has reached local ther-malization when the participant is large enough. Finally, we study the time evolution of elliptic flow and eccentricity. It is firstly observed that quark coalescence as hadronization scheme can reduce the momentum anisotropy of the system in the process of evolution.