Study On Collective Flow Features Of Net-proton And Strange Particles

With the running of Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider(LHC) , relativistic heavy ion collisions have been one of the most important research area. Several of the most important questions that RHIC and LHC should be answered are: what is the degree of thermalization of that LHC can reach? What is the situation of the produced matter to reach local equilibrium? How to express the thermalization feature of the system by using the thermalization quantity such as temperature, pressure and energy? What is the feature of the phase space of the material of high temperature and high density? How to investigate the equation of state and the transition between the hadron and QGP?and how to study the effect of collision on nuclear geometry ?The study of collective flow in high energy nuclear collisions has attracted increasing attentions from both experimental and theoretical points of view. The physics of longitudinal and transverse flows is due to their system evolution at early time and nuclear stopping. In general, the collective evolution of the hot and dense matter leaves a distinct imprint on the phase space distribution of the fireball at freeze-out. To disentangle such information from features generated during freeze-out, a refined understanding of the decoupling process is needed.Non-Uniform Flow Model (NUFM) realized that central dip of net proton distribution is closely related to the non-uniform feature of longitudinal phase space. As the incident energy increase, the transparency/stopping of relativistic heavy-ion collisions should be taken into account more carefully. A more reasonable assumption is that the fireballs keep some memory on the motion of the incident nuclei, and therefore the distribution of fireballs, instead of being uniform in the longitudinal direction, is more concentrated in the direction of motion of the incident nuclei, i.e. more dense at large absolute value of rapidity. It will not only lead to anisotropy in longitudinal-transverse directions, but also render the fireballs (especially for those baryons) distributing non-uniformly in the longitudinal direction. NUFM may analyze the central dip of baryon rapidity distribution by assuming that the centers of fireballs are distributed non-uniformly in the longitudinal phase space.We have ever used NUFM to study the net proton rapidity among AGS, SPS and RHIC energy regions. But for the RHIC energy regions, we made a mistake before to predict the distributions of net proton distributions since we neglected the effects of the baryon number conservation. Therefore, it is necessary to reanalyze the features of net proton rapidity distributions among AGS to RHIC by taking into account the baryon number conservation. It is found that when we consider the baryon number conservation, the features of the distributions at RHIC are completely different from the results given before , especially at large absolute rapidity region.With the run of forthcoming LHC, the predictions of the features of net proton rapidity distributions at LHC are also important. We will restudy the features of net proton rapidity distributions among AGS to RHIC by using NUFM, and make prediction for the features of forthcoming LHC in this paper.The strange particle distributions are also investigated by using NUFM during the SPS energy region. The dependence of the number of strange particles and the velocity of longitudinal flow on incident energies is also studied in this paper.