Model Study For Higher Moments Of Conserved Quantities In Relativistic Heavy Ion Collisions

At the beginning of twentieth century, scientists notice that the system is in a condition with high temperature and density when it in the initial time of heavy ion collision with high energy. In this condition the system may have a change called phase transition, which would cause hadron matter transfer to a new physical form called Quark Gluon Plasma(QGP). As a new matter, QGP drew a great attention to the leading edge of scientific research. As an important method in study about QGP, Heavy ion collider had been a significant development in research. Theory scientists point that Quantum Chromo Dynamic can describe the hardon interaction between quake and gluon well, and correctly predicted and explained lots of physical phenomenon on this basis. Phase transition from hadron phase to QGP can be described by QCD phase diagram well, which the abscissa and ordinate represent baryon chemical potential μB and temperature To, respectively. The first phase transition lies on the situation with low temperature and high μB, the point at the start of first phase transition boundary is called QCD critical point. After the critical point with the potential decreasing and temperature increasing is a cross over region between hardon phase to QGP, mapping the critical point have great significant for studying phase diagram.A lot of information can be revealed by the particles in final states in relativity heavy ion collision, conserve quantum is one of that. On theory, the fluctuation of conserve quantum distribution is in direct proportion to correlation length. Since the correlation length is discontinuous at the critical point, the fluctuation of conserve quantum is obvious at the critical point. It’s a powerful tool for searching critical point, the fluctuation of high moment can reveal the phase transition region. The relativistic heavy ion collision at Brookheaven National Lab was produced at different center of mass energy, which produced a high tempreture and high density circumstance, and made mapping critical point from experiment possible.In order to studying the nature of the net conserve quantum, we make the gold-gold collision with Ultra Relativistic Quantum Molecular Model at different energy. We measured the centrality and energy dependence of net conserve quantum distribution from final state. Since there was no phase transition phenomenon, when comparing model result with the result from the real experiment the deviation was obvious at low energy which had great significant to locating the critical point. Further more, we study the behavior of the distribution under the wider window of rapidity, it also can help us to understand the characteristics of net conserve quantum.