Dynamical fluctuations as a probe of QGP formation

Fluctuations depend on the properties of the system and may carry significant information about the intervening medium created in the collisions. Underlying dynamics of multiparticle production in relativistic nuclear collisions can be well understood by studying presence of fluctuations in these collisions. Dynamical fluctuations may arise due to some physical processes taking place in the collisions. As an after effect of the formation of QGP, the multiplicity and pseudorapidity distributions of the secondary particles may show large non-statistical fluctuations in some events. An event-by-event analysis of fluctuations will surely help in separating dynamical and statistical fluctuations. Experimental and theoretical understandings and information are merging together to relate the fluctuations with phase transition of the confined hadronic matter to QGP. The power law behaviour of scaled factorial moments (SFMs) on bin size is known as “intermittency”, which can predict the existence of dynamical fluctuations. Evidence of power law behaviour in experimental data of e+e- annihilation, -nucleus, hadron-hadron, hadron-nucleus and nucleus-nucleus collisions have been found. Thus, intermittency seems to be a general property of multiparticle production. No single mechanism has been found to explain the intermittency. For this purpose, two stacks of BR-2 emulsion exposed to 4.5A GeV/c silicon and carbon beams at Synchrophasotron of Joint Institute of Nuclear Research (JINR), Dubna, Russia, and also two stacks of Fuji type of emulsion exposed to 14.6A GeV/c at Alternating Gradient Synchrophasotron (AGS) of Brookhaven National Laboratory (BNL), NewYork, USA, have been utilized for data samples. The method of line scanning has been adopted to scan the stacks, which was carried out using Japan made NIKON (LABOPHOT and Tc-BIOPHOT) high resolution microscopes with 8 cm movable stage using 40X objectives and 10X eyepieces. The interactions due to beam tracks making an angle < 2 to the mean direction and lying in emulsion at depths > 35 m from either surface of the pellicles were included in the final statistics. Using the data samples of 701 events of 28Si-Em interactions, 844 events of 12C-Em interactions at 4.5A GeV/c and 915 events of 28Si-Em interactions at 14.6A GeV/c, we have studied the existence of event-by-event dynamical fluctuations by using the methods of scaled factorial moments (SFMs), Fq and modified multifractal moments, Gq. The experimental results have also been compared with correlated event generators FRITIOF and UrQMD models and also uncorrelated Lund Monte-Carlo model. The analysis of SFMs gives an evidence for an intermittency pattern of fluctuations and supports a self-similar cascade mechanism.

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