Multiplicity Distribution of Evaporated Fragments in Relativistic Nucleus-Nucleus Collisions

The multiplicity distribtuion of evaporated fragments in relativistic nucleus-nucleus collisions are discussed.The calculated results are in agreement with the exper-imental data in the energy range from 3.7 to 200 GeV/N.

A Calculation of Excitation Energy of Spectator in Relativistic Nucleus-Nucleus Collisions

The excited degree of spectator in relativistic nucleus-nucleus collisions is investig-ated.The heat of friction due to the relative motion beween the participant and the spectatorand the superfluous surface energy due to the spectator deformation are calculated.

Longitudinal Extension and Pseudorapidity Distributions of Shower Particles in Relativistic Nucleus-Nucleus Collisions

The longitudinal extension of interacting system in relativistic nucleus-nucleus colli-sions is considered.The pseudorapidity distribution of shower particles is described by the ther-realized cylinder picture.The calculated results are in agreement with the experimental data inthe incident energy region from 10~1 to 10~5 GeV/u.

Properties of collective flow and pion production in intermediate-energy heavy-ion collisions with a relativistic quantum molecular dynamics model

The relativistic mean-field approach was implemented in the Lanzhou quantum molecular dynamics transport model(LQMD.RMF). Using the LQMD.RMF, the properties of collective flow and pion production were investigated systematically for nuclear reactions with various isospin asymmetries. The directed and elliptic flows of the LQMD.RMF are able to describe the experimental data of STAR Collaboration. The directed flow difference between free neutrons and protons was associated with the stiffness of the symmetry energy, that is, a softer symmetry energy led to a larger flow difference. For various collision energies, the ratio between the π^(-) and π^(+) yields increased with a decrease in the slope parameter of the symmetry energy. When the collision energy was 270 MeV/nucleon, the single ratio of the pion transverse momentum spectra also increased with decreasing slope parameter of the symmetry energy in both nearly symmetric and neutron-rich systems.However, it is difficult to constrain the stiffness of the symmetry energy with the double ratio because of the lack of threshold energy correction on the pion production.

Electromagnetic fields in ultra-peripheral relativistic heavy-ion collisions

Ultra-peripheral heavy-ion collisions(UPCs)offer unique opportunities to study processes under strong electromagnetic fields.In these collisions,highly charged fast-moving ions carry strong electromagnetic fields that can be effectively treated as photon fluxes.The exchange of photons can induce photonuclear and two-photon interactions and excite ions.This excitation of the ions results in Coulomb dissociation with the emission of photons,neutrons,and other particles.Additionally,the electromagnetic fields generated by the ions can be sufficiently strong to enforce mutual interactions between the two colliding ions.Consequently,the two colliding ions experience an electromagnetic force that pushes them in opposite directions,causing a back-to-back correlation in the emitted neutrons.Using a Monte Carlo simulation,we qualitatively demonstrate that the above electromagnetic effect is large enough to be observed in UPCs,which would provide a clear means to study strong electromagnetic fields and their effects.

Collision off-axis position dependence of relativistic nonlinear Thomson inverse scattering of an excited electron in a tightly focused circular polarized laser pulse

This paper presents a novel view of the impact of electron collision off-axis positions on the dynamic properties and relativistic nonlinear Thomson inverse scattering of excited electrons within tightly focused, circularly polarized laser pulses of varying intensities. We examine the effects of the transverse ponderomotive force, specifically how the deviation angle and speed of electron motion are affected by the initial off-axis position of the electron and the peak amplitude of the laser pulse. When the laser pulse intensity is low, an increase in the electron's initial off-axis distance results in reduced spatial radiation power, improved collimation, super-continuum phenomena generation, red-shifting of the spectrum's harmonic peak, and significant symmetry in the radiation radial direction. However, in contradiction to conventional understandings,when the laser pulse intensity is relatively high, the properties of the relativistic nonlinear Thomson inverse scattering of the electron deviate from the central axis, changing direction in opposition to the aforementioned effects. After reaching a peak, these properties then shift again, aligning with the previous direction. The complex interplay of these effects suggests a greater nuance and intricacy in the relationship between laser pulse intensity, electron position, and scattering properties than previously thought.

Gluon saturation and net-proton spectra in relativistic nucleus-nucleus collisions

By means of the AKK08 fragmentation function, the net-proton transverse momentum （pT） spectra in A＋A collisions are studied with two phenomenological models based on the Color Glass Condensate formalism. After a χ2 analysis of the experimental data from BRAHMS, the normalization constant C is extracted at RHIC energies of √sNN =62.4 and 200 GeV, and the theoretical results of the net-proton pT spectra at selected rapidities are also given. It is shown that the theoretical results are in good agreement with the experimental data. Finally, assuming the constant C should have an exponent dependence of √sNN, we also predict the theoretical results of net-proton pT spectra at LHC energies of √sNN = 2.76, 3.94, and 5.52 TeV.

Slow Particle Production in Nucleus-Nucleus Collisions at Relativistic Energies

In this paper an effort has been made to study the general characteristics of slow particles produced in the interactions of 32S-Em at 200 AGeV to extract the information about the mechanism of particle production. The results have been compared with the experimental results obtained by other workers. The multiplicity distributions of the slow target associated particles (black, grey and heavy tracks) produced by 32S-beam with different targets have been studied. Also several types of correlations among them have been investigated. The variation of the produced particles with projectile mass number and target size has been studied. Also the multiplicity distributions of slow particles with NBD fits are presented and scaling multiplicity distributions of slow particles produced have been studied in order to check the validity of KNO-scaling.

Impact of initial fluctuations and nuclear deformations in isobar collisions

Relativistic isobar^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zrcollisions have revealed intricate differences in their nuclear size and shape,inspiring unconventional studies of nuclear structure using relativistic heavy ion collisions.In this study,we investigate the relative differences in the mean multiplicityR_(<Nch>)and the secondR_(ε2)and third-order eccentricityR_(ε3)between isobar collisions using initial state Glauber models.It is found that initial fluctuations and nuclear deformations have negligible effects on R_(<Nch>)in most central collisions,while both are important for the R_(ε2)and R_(ε3),the degree of which is sensitive to the underlying nucleonic or sub-nucleonic degree of freedom.These features,compared to real data,may probe the particle production mechanism and the physics underlying nuclear structure.

Search for the QCD critical point with fluctuations of conserved quantities in relativistic heavy-ion collisions at RHIC： an overview

Fluctuations of conserved quantities, such as baryon, electric charge, and strangeness number, are sensitive observables in relativistic heavy-ion collisions to probe the QCD phase transition and search for the QCD critical point. In this paper, we review the experimental measurements of the cumulants(up to fourth order) of event-byevent net-proton(proxy for net-baryon), net-charge and netkaon(proxy for net-strangeness) multiplicity distributions Au+Au collisions at sNN^(1/2) 7:7; 11:5; 14:5; 19:6; 27;39; 62:4; 200 Ge V from the first phase of beam energy scan program at the relativistic heavy-ion collider(RHIC). We also summarize the data analysis methods of suppressing the volume fluctuations, auto-correlations, and the unified description of efficiency correction and error estimation.Based on theoretical and model calculations, we will discuss the characteristic signatures of critical point as well as backgrounds for the fluctuation observables in heavy-ion collisions. The physics implications and the future secondphase of the beam energy scan(2019–2020) at RHIC will also be discussed.

Azimuthal distributions of final-state particles and fragments and transverse structure of emission source in high-energy nucleus-nucleus collisions

The azimuthal distributions of final-state particles and fragments produced in high-energy nucleus-nucleus collisions are described by a modified multisource ideal gas model which contains the expansions and movements of the emission sources. The transverse structures of the sources are given in the transverse plane by momentum components Px and Py, and described by parameters in the model. The results of the azimuthal distributions, calculated by the Monte Carlo method, are in good agreement with the experimental data in nucleus-nucleus collisions at high energies.

Effect of relaxation time on the squeezed correlations of bosons for evolving sources in relativistic heavy-ion collisions

The squeezed back-to-back correlation(SBBC)of a boson-antiboson pair is sensitive to the time distribution of the particle-emitting source,and the SBBC function for an evolving source is expected to be affected by the relaxation time of the system.In this study,we investigated the effect of relaxation time on the SBBC function.We propose a method for calculating the SBBC function with relaxation-time approximation for evolving sources.SBBC functions of D^(0)D^(-0)in relativistic heavy-ion collisions were investigated using a hydrodynamic model.We found that the relaxation time reduces the amplitudes of the SBBC functions.This becomes apparent for long relaxation times and large initial relative deviations of the chaotic and squeezed amplitudes from their equilibrium values in the temporal steps.

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.

Estimation of Local Energy Density in Relativistic Heavy-Ion Collisions

The energy density for the central region in relativistic heavy-ion collisions can be estimated via the pseudorapidity distribution of transverse energy.The way to estimate the local energy density for the central region in relativistic heavy-ion collisions is proposed,in which only final state particles emitted from the same source are included.The energy density arrived in the NA49 experiments is about 0.9 GeV/fm^(3).

An Explanation of a Phenomenon in Relativistic Heavy-Ion Collisions

The multi-source pion interferometry in relativistic heavy-ion collisions is presented and two-source models for hadron gas and hadron gas plus quark-gluon plasma are proposed. The models can resolve the HBT puzzle. For the same q and different direction of q, the two-pion correlation functions show characteristic oscillation behaviors, which may be used to distinguish the two-source models. Our research also showes that the multi-source pion correlations can resolve the HBT puzzle.

Nucleus-Nucleus Effects in Fully Differential Cross Sections for Energetic C6++He Collisions with Small Momentum Transfer

The modified Coulomb-Born approximation with and without the internuclear interaction （MCB-NN and MCB） is used to calculate the fully differential cross sections （FDCS） for the single ionization of helium by lOO MeV/amu C6＋ impact. The effects of the internuclear interaction on the FDCS are examined in geometries. The results are compared with experimental data and theoretical predictions from a three-body distorted-wave （3DW） model and a time-dependent close-coupling model. It is shown that the present MCB-NN results are in good agreement with the experiments in the scattering plane and the MCB results qualitatively reproduce the experimental structure outside the scattering plane. In particular, the MCB theory predicts the ＇double-peak＇ structure in the perpendicular plane.

A Theoretical Approach to Study J/Ψ Suppression in Relativistic Heavy Ion Collisions with Ellipsoidal Evolution

With a view to understanding J/Ψ suppression in relativistic heavy ion collisions, we compute the suppression rate within the framework of hy-drodynamical evolution model. For this, we consider an ellipsoidal flow and use an ansatz for temperature profile function which accounts for time and the three dimensional space evolution of the quark-gluon plas-ma. We have calculated the survival probability separately as the func-tion of transverse and longitudinal momentum. We have shown that previous calculations are special cases of this model.

Study of Wavelet Methodology and Chaotic Behavior of Produced Particles in Different Phase Spaces of Relativistic Heavy Ion Collisions

We applied the wavelet methodology for our earlier published research work of the chaotic behavior so called multiplicity fluctuations of secondary charged particles produced during the nucleus-nucleus (A-A) collisions at an energy of the order of ≈ 409 GeV in a new fashion. We illustrated the wavelet coherency in a relation of chaotic behavior for above said data of secondary charged pions in different phase spaces of collisions such as: η-space, φ-space (in one dimension) and ηφ-space (in two dimensions) respectively. We have shown the changes in the wavelet coherence when there are different values of two parameters “q” and “p”. We discussed our new results for the comparison purpose and findings were in the good agreements.

Emission of Protons in Inelastic Nucleus-Nucleus Collisions at High Energy

Based on the participant-spectator model and the analysis of particle producing proce-ss, the rapidity distribution and the noninvariant center-of-mass energy spectrum of final pro-tons produced in inelastic nucleus-nucleus collisions are studied.

Determination of Absorption Cross Section of J/ψ in Relativistic Heavy Ion Collisions

The absorption cross section σabs of J/ψ produced in relativistic heavy ioncollisions is deduced based on the analysis of the absorption length through which theproduced J/ψ passes in the colliding nuclei.The obtained σabs in A-A collisions is con-siderably higher than that in h-A processes.The reason for this different result is dis-cussed in terms of an analysis of the pT-dependence of the produced J/ψ.