124273608
Strange Quark Matter and Strangelets in a Strong Magnetic Field
We study the stability properties of magnetized strange quark matter and strangelets under a strong magnetic field in the MIT bag model. The free energy per baryon of strange quark matter feels a great influence from the magnetic held. At the held strength about 1017 G, the magnetized strange quark matter becomes more stable. Considering the finite size effect, the magnetic influence on strangelets becomes complicated. For a given magnetic held, there exists a critical baryon number, below which the magnetized strangelets have lower energy than the non-magnetized strangelets. For the held strength of 5 × 1017 G, the critical baryon number is Ac ~ 100. Generally, the critical baryon number increases with the decreasing external magnetic held. When the held strength is smaller than 1017 G, the critical baryon number goes up to Ac ~ 105. The stable radius, electric charge, and quark flavor fractions of magnetized strangelets are shown.
55102165
On Current Conversion between Particle Rapidity and Pseudorapidity Distributions in High Energy Collisions
In high energy collisions, one usually needs to give a conversion between the particle rapidity and pseudorapidity distributions. Currently, two equivalent conversion formulas are used in experimental and theoretical analyses. An investigation in the present work shows that the two conversions are incomplete. Then, we give a revision on the current conversion between the particle rapidity and pseudorapidity distributions.
120288217
Comparing two-Boltzmann distribution and Tsallis statistics of particle transverse momentums in collisions at LHC energies
The transverse momentum distributions of final-state particles produced in collisions at energies available at the Large Hadron Collider (LHC) are studied by using the two-Boltzmann distribution and Tsallis statistics. Experimental distributions described by the two-Boltzmann distribution can be described by the Tsallis statistics. The two-temperature emission described by the two-Boltzmann distribution reflects temperature fluctuation of interacting system. The Tsallis statistics can describe the temperature fluctuation and the degree of non-equilibrium. The results calculated by the two-Boltzmann distribution and the Tsallis statistics are in agreement with the experimental data available at the LHC energies. In some cases, the two-Boltzmann distribution degenerates to (single) Boltzmann distribution.
121546377
Dependences of charged particle pseudorapidity distributions on impact parameter and center-of-mass energy in nucleus–nucleus collisions at relativistic energies
The centrality and rapidity dependence of charged particles over a wide range of center-of-mass energy are analyzed. In this framework of participant-spectator model, the interacting system of nucleus–nucleus collisions at relativistic energies is divided into four parts (sources): target spectator, target participant, projectile participant and projectile spectator. Each source is treated by using a revised Landau model. The pseudorapidity distributions calculated by four-component Landau model are found to be in agreement with experimental data of the PHOBOS and ALICE collaborations. The distribution height is mainly determined by effective nucleon number and center-of-mass energy; and the distribution width being measured by the revised width in the Landau model and the sources rapidity shifts. Furthermore, we have found two empirical relations for projectile-participant and projectile-spectator (pseudo)rapidity as functions of the center-of-mass energy.
118223181
Emission of Shower Particles in High-Energy Neutrino-Emulsion Collisions
117876030
Azimuthal Distributions of Particles and Projectile Fragments Produced in High-Energy Nucleus-Nucleus Collisions
Azimuthal distributions of the particles and projectile fragments produced in high-energy nucleus-nucleus collisions are important measurements of collective motion and, in particular, the directed and elliptic flows. The flows reflect the anisotropy of transverse particle emission. When two nuclei collide at non-zero impact parameter, high pressure is developed at the impact. The matter will have a tendency to flow in the direction where the pressure gradient is larger. Since the discovery of flow [1, 2], a lot of experimental results have been obtained. The azimuthally anisotropic flow in nucleus-nucleus collisions at Bevalac/SIS energies has been studied in detail by the Plastic Ball experiment [3], EOS [4], FOPI [5], and KAOS [6] Collaborations. The E877 experiment was the first to extend flow measurements to energies above the Bevalac [7]. At AGS and SPS energies, the flow effects have now been studied by the E877 [8], E895 [9], E866/E917 [10], NA49 [11], and WA98 [12] Collaborations. Simultaneously, much theoretical work, e.g., [13, 14], has been devoted to understand the mechanism responsible for the flows. Let the beam direction be the oz axis and the reaction plane be the xoz plane. In the xoy plane, the azimuthal angle is defined by
119257866
Higher moments of net baryon distribution as probes of the QCD critical point
It is crucially important to find an acceptance and late collision process independent observable in searching for the possible critical point predicted by QCD. By utilizing a multiphase transport (AMPT) model and ultrarelativistic quantum molecular dynamics (UrQMD) model, we study the centrality and evolution time dependence of higher moments of net baryon distribution in Au+Au collisions at sq root(s{sub NN})=17.3 GeV. The results suggest that kurtosis and skewness are less sensitive to the acceptance effect and late collision process. Thus, they should be good observables providing the information on the early stage of a heavy-ion collision. In addition, our study shows that the product of kurtosis times sigma{sup 2} of the net proton distribution is quite different from that of the net baryon distribution when the collision energy is lower than sq root(s{sub NN})=20 GeV, the Monte Carlo calculations on kurtosiscentre dotsigma{sup 2} have a deviation from the theoretical predictions.
119107991
Transport model study of nuclear stopping in heavy-ion collisions over the energy range from 0.09A to 160A GeV
Nuclear stopping in heavy-ion collisions over a beam energy range from SIS and AGS up to SPS is studied in the framework of the modified Ultrarelativistic Quantum Molecular Dynamics transport model, in which mean field potentials of both formed and "preformed" hadrons (from string fragmentation) and medium-modified nucleon-nucleon elastic cross sections are considered. It is found that nuclear stopping is influenced by both the stiffness of the equation of state and medium modifications of nucleon-nucleon cross sections at SIS energies. At high SPS energies, a two-bump structure is shown in the experimental rapidity distribution of free protons, which can be understood by considering the preformed hadron potentials.
120587140
Scaling of the multiplicity distribution of evaporated fragments in oxygen-emulsion collisions at3.7AGeV