No Arabic abstract
By assuming the existing of memory effects and long-range interactions in the hot and dense matter produced in high energy heavy ion collisions, the nonextensive statistics together with the relativistic hydrodynamics including phase transition is used to discuss the transverse momentum distributions of charged particles produced in heavy ion collisions. It is shown that the combined contributions from nonextensive statistics and hydrodynamics can give a good description to the experimental data in Au+Au collisions at sqrt(s_NN )= 200 GeV and in Pb+Pb collisions at sqrt(s_NN) )= 2.76 TeV for pi^(+ -) , K^(+ -) in the whole measured transverse momentum region, and for p(p-bar) in the region of p_T<= 2.0 GeV/c. This is different from our previous work, where, by using the conventional statistics plus hydrodynamics, the describable region is only limited in p_T<= 1.1 GeV/c.
It has long been debated whether the hydrodynamics is suitable for the smaller colliding systems such as p+p collisions. In this paper, by assuming the existence of longitudinal collective motion and long-range interactions in the hot and dense matter created in p+p collisions, the relativistic hydrodynamics incorporating with the nonextensive statistics is used to analyze the transverse momentum distributions of the particles. The investigations of present paper show that the hybrid model can give a good description of the currently available experimental data obtained in p+p collisions at RHIC and LHC energies, except for p and p^bar produced in the range of p_T> 3.0 GeV/c at sqrt(s)=200 GeV.
The charged particles produced in heavy ion collisions consist of two parts: One is from the freeze-out of hot and dense matter formed in collisions. The other is from the leading particles. In this paper, the hot and dense matter is assumed to expand according to the hydrodynamic model including phase transition and decouples into particles via the prescription of Cooper-Frye. The leading particles are as usual supposed to have Gaussian rapidity distributions with the number equaling that of participants. The investigations of this paper show that, unlike low energy situations, the leading particles are essential in describing the pseudorapidity distributions of charged particles produced in high energy heavy ion collisions. This might be due to the different transparencies of nuclei at different energies.
Descriptions of heavy-ion collisions at Fermi energies require to take into account in-medium dissipation and phase-space fluctuations. The interplay of these correlations with the one-body collective behaviour determines the properties (kinematics and fragment production) and the variety of mechanisms (from fusion to neck formation and multifragmentation) of the exit channel. Starting from fundamental concepts tested on nuclear matter, we build up a microscopic description which addresses finite systems and applies to experimental observables.
We discuss the rapidity distribution of produced jets in heavy-ion collisions at LHC. The process allows one to determine to a good accuracy the value of the impact parameter of the nuclear collision in each single inelastic event. The knowledge of the geometry is a powerful tool for a detailed analysis of the process, making it possible to test the various different elements which, in accordance with present theoretical ideas, take part to the production mechanism.
We analyze the transverse momentum distribution of $J/psi$ mesons produced in Au + Au collisions at the top RHIC energy within a blast-wave model that accounts for a possible inhomogeneity of the charmonium distribution and/or flow fluctuations. The results imply that the transverse momentum spectra of$J/psi$, $phi$ and $Omega$ hadrons measured at the RHIC can be described well if kinetic freeze-out takes place just after chemical freeze-out for these particles.