Δ—scaling and Information Entropy in Ultra—Relativistic Nucleus—Nucleus Collisions

The Δ-scaling method has been applied to ultra-relativistic p p,C C and Pb Pb collision data simulated using a high-energy Monte Carlo package,LUCIAE 3.0.The Δ-scaling is found to be valid for some physical variables,such as charged particle multiplicity,strange particle multiplicity and number of binary nucleon-nucleon-nucleon collisions from these simulated nucleus-nucleus collisions over an extended energy ranging from E1ab=20 to 200A GeV.In addition we derive the information entropy from the multiplicity distribution as a function of beam energy for these collisions.     

Centrality Dependence of Flow in High—Energy Nucleus—Nucleus Collisions

Directed flow and elliptic flow of final state particles in high-energy nucleus-nucleus collisions in the EMU01 experiment have been studied.The dependences of directed flow and elliptic flow on incident energy and impact centrality of outgoing particles are presented.The results exhibit strong dependence of flow on centrality and energy.We also suggest a more reliable way to determine the event plane resolution here.     

Chiral Effects in Nucleus–Nucleus Collisions: Experimental Review

A survey of experimental results obtained by studying chiral effects in nucleus–nucleus collisions at various energies is presented. The entire body of these experimental results confirms indirectly a topologically nontrivial structure of the QCD vacuum and the possibility of a local violation of discrete QCD symmetries at finite temperature. A significant decrease in the asymmetry of the distribution of electrically charged particles with respect to the reaction plane in heavy-ion collisions in the energy range of \(\sqrt {sNN} \) GeVmay be indicative of a possible transition to the region where hadron states dominate over quark–gluon degrees of freedom in a mixed phase formed in nucleus–nucleus collisions at intermediate energies.     

In-Medium Kaon Potential and Nuclear Equation of State Measured in Nucleus–Nucleus Collisions

The kaon production in heavy ion collisions at intermediate energies provides a sensitive probe to study the in-medium properties and nuclear equation of state of hadrons. Properties of kaons in dense hadronic matter are important for a better understanding of both, the possible restoration of chiral symmetry in dense hadronic matter and the properties of nuclear matter at high densities. We investigated the in-medium kaon potential and nuclear equation of state by transverse mass spectra of K ⁺ mesons in heavy ion collisions. We use quantum molecular dynamics (QMD) models based on covariant kaon dynamics to simulate ${_{28}^{58}Ni +_{28}^{58}Ni}$ collisions at 1.93 A GeV, to analyze the transverse mass spectra of K ⁺. Calculated results with a repulsive in-medium K ⁺N potential can reasonably describe the features of KaoS data. They also shown that the transverse mass spectrum of K ⁺ mesons is a sensitive observable to probe the kaon in-medium potential in dense nuclear matter.     

Development and Construction of Track and Identification Systems for Experiments Aimed at Studying Extreme Properties of Nuclear Matter in Nucleus–Nucleus Collisions

Physics of Atomic Nuclei - Investigation of properties of nuclear matter at extremely high temperature and/or extremely high baryon densities under laboratory conditions is one of the fundamental...     

Transverse Momentum Distribution of Final State π in Relativistic Heavy Ion Collisions

Using hydrodynamical model of transverse expansion,we investigate the transverse momentum distribution of the final state π on ¹⁶O－Au collisions.When the constituent influence of the gas is taken into account the calculated result fits the NA35 data better than that of D.Knsnezov's.     

Measurement of Parameters of Neutral Mesons Produced in Meson–Nucleus Interactions in Hyperon-M Experiment

Physics of Atomic Nuclei - According to modern theories, the parameters of neutral mesons such as their mass and width are closely connected with the medium in which the mesons are present....     

Squeezed Back-to-Back Correlation of D~0~0 in Relativistic Heavy-Ion Collisions

We investigate the squeezed back-to-back correlation(BBC) of D~0~0 in relativistic heavy-ion collisions, using the in-medium mass modification calculated with a self-energy in hot pion gas and the source space-time distributions provided by the viscous hydrodynamic code VISH2+1. It is found that the squeezed BBC of D~0~0 is significant in peripheral Au+Au collisions at the relativistic heavy ion collider energy. A possible way to detect the squeezed BBC in an experiment is presented.     

Polarization Conversion of Single Photon via Scattering by a Λ System in a Semi-Infinite Waveguide

We theoretically investigate single-photon polarization conversion via scattering by an atom with Λ configuration coupled to a semi-infinite waveguide and discuss the two cases in which the Λ system is non-degenerated and degenerated. By applying the hard-wall boundary condition of the semi-infinite waveguide, it is found that singlephoton polarization conversion can be realized with unit probability for both cases under the ideal condition.Together with the polarization conversion, the frequency conversion of a single photon can also be realized with unit probability in the ideal case if the Λ system is not degenerated.     

Transverse Momentum and Rapidity Distributions of Φ Mesons Produced in Pb-Pb Collisions at SPS Energies

To investigate the excitation degree of the interacting system and the penetrating power of the projectile nucleus and to understand their dependences on incident energy, the transverse momentum and rapidity distributions of particles produced in nucleus-nucleus collisions at high energies are studied by using a multisource ideal gas model. The calculated results are compared with the most recent NA49 experimental data of φ mesons produced in Pb-Pb collisions at the Super Proton Synchrotron （SPS） energies.     

Λ Production and Λ/p Ratio in Relativistic Heavy Ion Collisions

The Λ multiplicity and Λ/p ratio are studied by hadron transportation-string fragmentation model in relativistic heavy ion collisions. Firstly, the dependence of Λ multiplicity and Λ/p ratio on the system size and the collision centrality is studied. It shows that the Λ and p multiplicities go up as the increase of system size and the increase of collision centrality. However, their ratio keeps almost a constant. The effect of Λ annihilation cross section to Λ multiplicity and Λ/p ratio is also studied. It is found that this effect is weak: Λ multiplicity and Λ/p ratio have a little amount of increase by the decrease of Λ annihilation cross section. Even the cross section is down to zero, Λ/p ratio is only 1.2 in 200A GeV AuAu head on collision. The Λ/p ratio is obtained to be 0.28 in pp collision, lying in the range of experimental data:0.2—0.3. It is also obtained that the ratio in AA collisions is 3—5 times of that in pp collision.     

Polarization Features of the 24Mg(2+) Nucleus Produced in the Reaction 27Al(p, α)24Mg(2+)

At the proton energy of E_p = 7.4 MeV, the double-differential cross sections for the reaction ²⁷Al(p, α₁γ)²⁴Mg were measured for 11 values of the alpha-particle emission angle in the range of θ_α = 30°–160°(lab). All even components of the density-matrix spin-tensors were reconstructed for the oriented ²⁴Mg nucleus in the 2⁺ state at 1.369 MeV, and the polarization features of this nucleus, including the populations of magnetic sublevels of the nucleus for all spin projections, multipole-moment orientation tensors, and the quadrupole and hexadecapole tensor polarizations, were determined. Relevant experimental results were compared with their counterparts calculated for the triton-pickup mechanism within the coupled-channel method and in the statistical limit of the compound-nucleus model.

     

Comparison of Models of Nucleus–Nucleus Interactions Implemented in CORSIKA

Physics of Atomic Nuclei - Four most widely used models of hadronic interactions at high energies implemented in CORSIKA program were compared basing on the simulation of the first...     

One-Dimensional Relativistic Problems on the Bound States and Degradation for a Superposition of Two δ Potentials

For a superposition of two potentials, exact one-dimensional wave functions of the bound states with quantization conditions and exact wave functions of the degradation state with transmission and reflection coefficients have been found. The phenomenon of complete reflection taking place for potentials of this type is investigated.     

Thermalization of Quark Matter Produced at the Highest Energy of a Relativistic Heavy-Ion Collider

Thermalization of quark matter is studied via a transport equation, which includes triple-quark elastic scattering amplitudes calculated in perturbative QCD. The triple-quark scatterings are demonstrated to be important for an anisotropic initial quark distribution produced in central Au-Au collisions at √sNN= 200 GeV. By examining momentum isotropy to which the transport equation leads, we can determine a thermalization time of 2.2fm/c for quark matter itself to thermalize by the two-quark and the triple-quark elastic scatterings. Meanwhile, an initial thermal quark distribution function is obtained.     

An Enhancement of Formation of Unstable 8Be Nucleus with the Growth of α-Particle Multiplicity in Fragmentation of Relativistic Nuclei

Physics of Atomic Nuclei - In this paper, the correlation between the formation of the unstable 8Be nucleus and accompanying α particles in the fragmentation of relativistic 16О, 22Ne,...     

The K+/π+ Ratio in High Energy Nucleus Collisions and the Effect of Secondary Collisions

We calculate the effect of secondary collisions in the K⁺/π⁺ ratio by an eikonal approximation and find that the secondary collisions are important.