Event-by-event analysis of maximum pseudo-rapidity gap fluctuation in high-energy nucleus-nucleus collisions

Abstract

PACS No. 25.75.-q 25.75.Ag. 25.75.Gz. 24.60.Ky. Abstract A detailed study of event-by-event maximum pseudo-rapidity gap fluctuations in relativistic heavy-ion collisions in terms of the scaled variance has been carried out for 16 O-AgBr, 28 Si-AgBr and 32 S-AgBr interactions at an incident momentum of 4.5 AGeV/c applying the multiplicity cut (N > . For all the interactions the values of scaled variance are found to be greater than zero indicating the presence of strong fluctuation of maximum rap gap values in the multiparticle production process. The event by event fluctuations are found to decrease with the increase of average multiplicity of the interactions. Experimental analysis has been compared with the results obtained from the analysis of events simulated by generating random numbers (MC-RAND events) and also by Ultra Relativistic Quantum Molecular Dynamics (UrQMD) model. UrQMD model simulated values of event by event fluctuations of maximum rapidity gap are less than the corresponding experimental values.

Event-by-event fluctuations of maximum particle density with respect to the width of the pseudo-rapidity interval at a few A GeV/c

“…Taking Ag and Br nuclei as target, events were generated separately for each target. According to the proportional abundance of Ag and Br nuclei present in the nuclear emulsion, the generated events were mixed with each other in order to get the desired UrQMD data sample [42]. All the charged mesons produced in the UrQMD simulation were considered for the analysis of event by event fluctuation of maximum particle density.…”

“…In nuclear emulsion detector sources of systematic errors are the scanning procedure, fading of tracks and the presence of background 10 contaminations. It has been discussed in our earlier papers that total contribution of systematic errors coming out from the scanning procedure, fading of tracks, and presence of background contaminations is around (1-2)% [42,45,52]. It has been discussed in [50] that the shower particles are mostly pions (more than 90%) with a small proportion (less than 10%) of kaons and hyperons among them.…”

“…One of the advantages of this detector is that it can record and store the information permanently about the charged particles with different ionizing power over the 4π geometry. Due to high spatial and good angular resolution (~0.1mrad) emulsion detector is quite acceptable for studying event by event fluctuation of the produced particles when they are distributed in a small phase space interval [41][42].…”

“…In order to get the required data for the present analysis NIKFI-BR2 emulsion pellicles of dimension 20cm 10 cm  600  m were irradiated by the 16 O, 28 Si and 32 S beam at 4.5 AGeV/c obtained from the Synchrophasatron at Joint Institute of Nuclear Research (JINR), Dubna, Russia [41][42]. When a projectile collides with the target an interaction or an event occurs.…”

“…Our analysis has been carried out for the interactions with the AgBr target only. For this study, we have selected 1057 events of 16 O-AgBr, 514 events of 28 Si-AgBr and 434 events of 32 S-AgBr interactions [41][42]. The present analysis has been performed on shower particles only.…”