Strange particle production in relativistic nucleus-nucleus collisions at RHIC and LHC energy regions

PACIAE, a parton and hadron cascade model, is utilized to systematically investigate strange particle production and strangeness enhancement in Au＋Au collisions and in Pb＋Pb collisions with the √SNN = 200 GeV at the RHIC and 2.76 TeV at the LHC, respectively. The experimental results at different centralities, using data from the STAR collaboration and the ALICE collaboration, are well described by the PACIAE model. This may represent the importance of the parton and hadron rescatterings, as well as the reduction mechanism for strange quark suppression, that are implemented in the PACIAE model.     

Study of Kinetic Freeze-Out Parameters as a Function of Rapidity in pp Collisions at CERN SPS Energies

We used the blast wave model with the Boltzmann–Gibbs statistics and analyzed the experimental data measured by the NA61/SHINE Collaboration in inelastic (INEL) proton–proton collisions at different rapidity slices at different center-of-mass energies. The particles used in this study were π+, π−, K+, K−, and p¯. We extracted the kinetic freeze-out temperature, transverse flow velocity, and kinetic freeze-out volume from the transverse momentum spectra of the particles. We observed that the kinetic freeze-out temperature is rapidity and energy dependent, while the transverse flow velocity does not depend on them. Furthermore, we observed that the kinetic freeze-out volume is energy dependent, but it remains constant with changing the rapidity. We also observed that all three parameters are mass dependent. In addition, with the increase of mass, the kinetic freeze-out temperature increases, and the transverse flow velocity, as well as kinetic freeze-out volume decrease.     

Effects of inelastic (re)scattering processes s→gg and gg→s on strange hadron production in pp collisions at RHIC and LHC energies

The rapidity densities at mid-rapidity and the transverse momentum distributions for strange hadrons produced in pp collisions are analyzed using the modified PACIAE model by considering the effect of inelastic (re)scattering processes s→gg and gg→s in parton (re)scattering. The calculated results of the transverse momentum spectra of the strangeness fitting with data measured by STAR and ALICE Collaborations can be improved, especially at large transverse momentum levels. This demonstrates that the effect of inelastic (re)scattering processes of s→gg and gg→s is not negligible at RHIC and LHC energy levels.     

Full and Partial Thermalization of Nucleons in Relativistic Nucleus-Nucleus Collisions

We propose a mechanism of thermalization of nucleons in relativistic nucleus-nucleus collisions. Our model belongs, to a certain degree, to the transport ones; we consider the evolution of the system, but we parametrize this development by the number of collisions of every particle in the system rather than by the time variable. We based on the assumption that the nucleon momentum transfer after several nucleon-nucleon (-hadron) collisions becomes a random quantity driven by a proper distribution.     

The simulations of Ca-Ca collisions: Binary break-up, onset of multifragmentation and vaporization

The incomplete fusion, onset of multifragmentation and vaporization is studied in Ca-Ca collisions at bombarding energies between 20–1000 A MeV and at impact parameters between b=0 to b _max using quantum molecular dynamics model. We find incomplete fusion events at E/A=20 MeV. The light mass fragment production at a given incident energy does not show any rise and fall with a change in the impact parameter. Whereas, the IMF production at higher energies (≥ 150 A MeV) has a clear rise and fall.     

Local charge compensation in the quark-cascade jet-production model

The charge correlations and the local charge compensation mechanism in rapidity space for quark jets are analysed in the framework of the quark-cascade jet-production model. The calculated results are compared with those observed experimentally in antineutrino-nucleon processes, and for the short range charge correlations observed ine ⁺ e ⁻ annihilation experiments. The results appear consistent with the quark-cascade model. The treatment of Snider (1975) is essentially based on Chew and Pignotti (1968). Pinskyet al (1973) showed the similarity of multiperipheral and Muller-Regge concepts.     

GROUP OF TRANSFORMATIONS WITH RESPECT TO THE COUNTERPART OF RAPIDITY AND RELATED FIELD EQUATIONS

The Lorentz-group of transformations usually consists of linear transformations of the coordinates, keeping as invariant the norm of the four-vector in (Minkowski) space-time. Besides those linear transformations, one may construct different forms of nonlinear transformations of the coordinates keeping unchanged that respective invariant. In this paper we explore nonlinear transformations of second-order which have a natural interpretation within the framework of Yamaleev's concept of the counterpart of rapidity (co-rapidity). The purpose of developed concept is to show that the formulae for energy and momentum of the relativistic particle become regular near the zero-mass and speed of light states. Furthermore, in a covariant formulation, the co-rapidity is presented as a four-vector which admits an extension of the Lorentz-group of transformations. In this paper we additionally show, that in the same way as the rapidity is related to the electromagnetic field, the co-rapidity is related to the field of strengths, which are given by a four-vector. The corresponding equations of such a field are also constructed.     

158A GeV的相对论重离子碰撞的强子快度分布及温度拟合

针对最近NA49在158A GeV的实验(C+C,Si+Si,Pb+Pb)数据,应用LUCIAE3.0模型进行模拟,得到了强子的快度分布和横向动量分布,并与实验数据进行比较,发现基本与实验数据相吻合。并对横向动量分布进行温度拟合,给出了和实验数据吻合很好的结果,但是对于重系统或重强子LUCIAE3.0给出的结果与实验符合相对较差.     

Hadronic rapidity spectra in heavy ion collisions at SPS and AGS energies in a quark combination model

The quark combination mechanism of hadron production is applied to nucleus-nucleus collisions at the CERN Super Proton Synchrotron (SPS) and the BNL Alternating Gradient Synchrotron (AGS). The rapidity spectra of identified hadrons and their spectrum widths are studied. The data of π^-, K^±, φ, Λ, Λ, Ξ^- and Ξ⁺ at 80 and 40 A GeV, and in particular at 30 and 20 A GeV where the onset of deconfinement is suggested to happen, are consistently described by the quark combination model. However, at AGS 11.6 A GeV below the onset, the π^±, K^± and Λ spectra cannot be simultaneously explained, indicating the disappearance of the intrinsic correlation of their production in the constituent quark level. The collision-energy dependence of the rapidity spectrum widths of the constituent quarks, and the strangeness of the hot and dense quark matter produced in heavy ion collisions, are obtained and discussed.     

Centrality,azimuthal and rapidity dependence of two-particle transverse-momentum correlation in relativistic heavy ion collisions

The centrality, azimuthal and rapidity dependence of two-particle transverse-momentum correlations are studied for Au-Au collision at 200 GeV using RQMD （relativistic quantum molecular dynamics） with and without final hadron re-scattering models. The influences of the re-scattering effects on the measured correlations are discussed. The results are compared with those from current heavy ion experiments.