Research On Rapidity And Scaling PT Distributions In Au+Au Collisions At RHIC

Particle distribution is one of the most important observables in high energy collisions. The research of the particle distribution is significantly important for understanding the evolution of the high energy heavy ion collision and the particle production mechanisms.We consider the transverse momentum and pseudo-rapidity distributions of particles in Au+Au collisions at 200 Gev. Based on the the transverse momentum distribution of particles of a species h produced at polar angleθ=π/2 in high energy proton-proton (p+p) collisions and nuclear stopping effect, a simple parameterization is suggested for the particle distribution. Compared to the experimental data, the agreement is very good. We can investigate the centrality dependence of rapidity distributions based on the parameterization obtained from fitting the data.Recently, the scaling behavior in the high energy collisions is getting more and more attentions. With the experimental data from STAR, PHENIX and BARHMS on the the centrality and rapidity dependence of the pT spectrum in Au+Au and d+Au collisions, we show that there exists a scaling behavior which is independent of the colliding system, centrality and (pseudo)rapidity forπ.In the same way, we show that there also exists a scaling distribution for proton and anti-proton, independent of the centrality and rapidity in Au+Au collisions at 200 GeV. There is a little difference between the scaling functions for the proton and antiproton, but they are very different from that forπ's. It is not surprising, because the distribution reflects the particle production dynamics which may be different for different particles.Statistical model have been often applied to hadron physics. We can derive the particle distribution from some statistical consideration. Considering the complex nonlinear interactions and the possible presence of fractal chaotic behavior in nuclear collisions, A non-extensive entropy is used to derive the scaling function, based on the principle of maximum entropy. According to the discussion, we find that the produced particle system may be a non-extensive fractal system and the fractal property is independent of the colliding system.We predict that the scaling function is different for different particles. It is correct forπ, proton and anti-proton, but what about kaon and hyperon (Λ,Ξ)? This is under consideration. From the scaling behavior, we can get more information about the particle production mechanisms. Obviously more detailed studies, both theoretically and experimentally are needed.