An investigation of bin–bin correlation by the method of factorial correlator in high-energy heavy ion collisions

This paper presents a study of bin–bin correlation of the produced shower particles in the pseudo-rapidity space by the method of factorial correlator in [Formula: see text]O-AgBr and [Formula: see text]S-AgBr interactions at 4.5[Formula: see text][Formula: see text]GeV/[Formula: see text]. The correlated moments are found to increase with decreasing bin–bin separation D, following a power law. Strong bin–bin correlation is exhibited by the experimental data. Experimental data also supports the validity of log normal approximation. Experimental analysis has been compared with the results obtained from the analysis of events simulated by UrQMD model.

A study of genuine pion correlations and fluctuations in relativistic nucleus–nucleus collisions

In this study, we have performed a detailed analysis of genuine pion correlations and fluctuations in terms of the normalized factorial comulant moments of second and third orders, [Formula: see text] and [Formula: see text], in case of [Formula: see text]O–AgBr interactions at [Formula: see text][Formula: see text]A and [Formula: see text][Formula: see text]A GeV/c. The experimental results are compared with the predictions of AMPT and UrQMD model simulated events. The UrQMD model reproduces the trends in experimental results but the strength of correlation is much smaller. However, the AMPT model does not also replicate all features of the experimental data. The genuine two-particle and three-particle correlations are found to become weaker with the increase in momentum of the projectile nucleus.

Spectral temperature of π− mesons in proton–carbon interactions at 4.2 GeV/c in the framework of UrQMD model

Transverse momentum [Formula: see text] spectra of [Formula: see text] mesons calculated using ultra-relativistic quantum molecular dynamic (UrQMD) model (Latest version 3.3-p2) simulations have been compared with [Formula: see text] spectra of [Formula: see text] mesons, obtained experimentally in interactions of protons beam with carbon nuclei (propane as target) at momentum of 4.2 GeV/c. Spectral temperatures of negative pions obtained in experimental and UrQMD model simulated interactions of protons beam with carbon nuclei have been calculated by fitting both spectra with four different fitting functions, i.e. Hagedorn thermodynamic, Boltzmann distribution, Gaussian and exponential functions. These functions are used commonly for describing hadron spectra and their spectral temperatures. Hagedorn thermodynamic function has been recommended as the most suitable function to extract the temperature of negative pions at above momentum among these four functions.

Centrality Dependence of Multiplicity Fluctuations in Ion-Ion Collisions from the Beam Energy Scan at FAIR

Multiplicity distributions and event-by-event multiplicity fluctuations in AuAu collisions at energies in future heavy-ion experiment at the Facility for Anti-proton and Ion Research (FAIR) are investigated. Events corresponding to FAIR energies are simulated in the frame work of Ultra Relativistic Quantum Molecular Dynamics (URQMD) model. It is observed that the mean and the width of multiplicity distributions monotonically increase with beam energy. The trend of variations of dispersion with mean number of participating nucleons for the centrality-bin width of 5% are in accord with the Central Limit Theorem. The multiplicity distributions in various centrality bins as well as for full event samples are observed to obey Koba, Nielsen and Olesen (KNO) scaling. The trends of variations of scaled variance with beam energy are also found to support the KNO scaling predictions for larger collision centrality. The findings also reveal that the statistical fluctuations in 5% centrality-bin width appear to be under control.

Estimation of pion-emitting source in symmetric and asymmetric collisions using the UrQMD model

The femtoscopy technique allows one to measure spatial and temporal characteristics of the particle-emitting source produced in high-energy collisions. In non-central ultrarelativistic heavy-ion collisions the emission source can be tilted in the reaction plane. In the current analysis, the orientation of freeze-out distributions with respect to the first-order event plane in symmetric (Au+Au) and asymmetric (Cu+Au) collisions at $$\sqrt {{s_{NN}}} = 200$$ GeV was studied using the UrQMD model to extract information about the emission source tilt. The effect of the initial geometry on the femtoscopic radii of small systems was measured at the same number of charged particles and transverse momentum was studied in d+Au and 3He+Au collisions at $$\sqrt {{s_{NN}}} = 200$$ GeV. The implications of the results are discussed.