Event-by-Event Particle Ratio Fluctuations at LHC Energies

A Monte Carlo study of identified particle ratio fluctuations at LHC energies is carried out in the framework of HIJING model using the fluctuation variable ν dyn . The simulated events for Pb-Pb collisions at s N N = 2.76 and 5.02 TeV and Xe-Xe collisions at s N N = 5.44 TeV are analyzed. From this study, it is observed that the values of π , K , p , K , and π , p follow the similar trends of energy dependence as observed in the most central collision data by NA49, STAR, and ALICE experiments. It is also observed that ν dyn for all the three combinations of particles for semicentral and central collisions, the model predicted values of ν dyn A , B for Pb-Pb collisions at s N N = 2.76 TeV agree fairly well with those observed in the ALICE experiment. For peripheral collisions, however, the model predicted values of ν dyn π , K are somewhat smaller, whereas for p , K and π , p it predicts larger values as compared to the corresponding experimental values. The possible reasons for the observed differences are discussed. The ν dyn values scaled with charged particle density when plotted against N part exhibit a flat behaviour, as expected from the independent particle emission sources. For p , K and π , p combinations, a departure from the flat trend is, however, observed in central collisions in the case of low p T window when the effect of jet quenching or resonances is considered. Furthermore, the study of ν dyn A , B dependence on particle density for various collision systems (including proton-proton collisions) suggests that at LHC energies ν dyn values for a given particle pair are simply a function of charged particle density, irrespective of system size, beam energy, and collision centrality.

EXPERIENCE OF OBTAINING THE PLAN OF EXPERIMENTS, WITH USING MODELS OF INTERACTION OF CHARGED PARTICLES

In this article a method of obtaining an experiment plan in a fragment of multidimensional space is analyzed and improved. The method is based on an assumption that particles will distribute evenly in an infinite space with constant charged particle density. To obtain the experiment plan, the infinite multidimensional space is replaced with a hypercube whose surface models influence of the surrounding infinite space. Software is developed and practical results in obtaining experiment plan in two-dimensional space are acquired. Two-dimensional space allows developing of a methodology and algorithm for obtaining experiment plan while providing a simple visualization of the solution. Acquired results in two-dimensional space give an opportunity to create methods for obtaining experiment plan in a hypercube of multidimensional space.

Geometry and Space-Time Extent of Pion Emission Region at FCC Energies

The energy dependence is investigated for a wide set of space-time characteristics derived from Bose–Einstein correlations of secondary pion pairs produced in proton-proton and nucleus-nucleus interactions. Analytic functions suggested for smooth approximations of the energy dependence of emission region parameters demonstrate reasonable agreement with all available experimental results for proton-proton collisions while the approximations correspond to most of experimental data for nucleus-nucleus collisions at energies above 5 GeV. Estimations for a wide set of space-time quantities are obtained for energies for the Future Circular Collider (FCC) project based on the smooth approximations. The space particle densities at freeze-out are derived also from estimations for the volume of the emission region and for total multiplicity at FCC energies. Estimations for charged particle density and its critical value allow the possibility of lasing behavior for secondary pions in nucleus-nucleus collisions at FCC energy. The mathematical formalism is presented for study of the peak shape of correlation function for general case of central-symmetrical Lévy–Feldheim distribution.

MULTIFRACTAL ANALYSIS OF CHARGED PARTICLE DISTRIBUTION IN 28Si-Ag/Br INTERACTION AT 14.5A GeV

The multifractal structure of one dimensional charged particle density distribution in 28 Si-Ag / Br interactions at 14.5 GeV per nucleon is investigated by using two different techniques. The experimental measurements are compared with a microscopic transport model of particle production based on the Ultra-relativistic Quantum Molecular Dynamics (UrQMD). Various parameters related to multifractality, for example the Lévy's index, are obtained. Our analysis shows that multifractal structure is present both in the experiment as well as in the simulation. As far as the self-similar nature of the density fluctuation is concerned, there exists, however, a small but definite quantitative difference between the two.

Intermittency and erraticity of charged particles produced in 28Si-Ag/Br interaction at 14.5 A GeV

In this paper, we present the intermittency and the erraticity analyses of the distributions of charged particles produced in 28Si-Ag/Br interaction at incident energy 14.5 A GeV. The experimental results are compared with a Monte Carlo simulation using ultra-relativistic quantum molecular dynamics (UrQMD) model. The experimental data show the presence of a nonstatistical component in the produced charged-particle density. Neither the UrQMD simulation nor the purely statistical simulation was found to match the experimental data. The present set of results are compared to those obtained in similar measurements from earlier high-energy nucleus–nucleus experiments.