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

Abstract

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. PACS numbers: 25.75.q, 25.75.Gz KEY-WORDS: Beam Energy Scan, Event-by-event fluctuations, Relativistic heavy-ion collisions.

Energy and system size dependence of strongly intensive fluctuation measures in heavy-ion collisions at FAIR energies

“…, is taken into account, where σ tot denotes the total cross section. Two colliding nuclei are described by Fermi gas model and hence the initial momentum of each nucleon is taken at random between zero and Thomas Fermi momentum [17,27]. The interaction term includes more than 50 baryon and 45 meson species [3].…”

“…The model has been successfully applied to study the thermalization [30], particle yields [31,32], leptonic and photonic probes [33] and ebe fluctuations [34][35][36][37][38][39]. Although the phase transition from hadronic to partonic phases are not explicitly included in the model, yet the study is expected to help in the interpretation of the experimental data as it would allow subtraction of simple dynamical and geometrical effects from the expected QGP signals [27,40].…”