Correlations and Event-by-Event Fluctuations in High Multiplicity Events Produced in 208Pb-208Pb Collisions

Analysis of high multiplicity events produced in 158A GeV/c 208Pb-208Pb collisions is carried out to study the event-by-event fluctuations. The findings reveal that the method of scaled factorial moments can be used to identify the events having densely populated narrow phase space bins. A few events sorted out by adopting this approach are individually analyzed. It is observed that these events do exhibit large fluctuations in their pseudorapidity, η, and azimuthal angle, ϕ, distributions arising due to some dynamical reasons. Two-particle Δη-Δϕ correlation study applied to these events too indicates that some complex two-dimensional structure of significantly high magnitude is present in these events which might have some dynamical origin. The findings reveal that the method of scaled factorial moments may be used as an effective triggering for events with large dynamical fluctuations.

New baryonic and mesonic observables from NA61/SHINE

One of the main objectives of the NA61/SHINE experiment at the CERN SPS is to study properties of strongly interacting matter. This paper presents new results on observables relevant for this part of the NA61/SHINE programme. These include the first ever measurements of ϕ meson production in p+p collisions at 40 and 80 GeV, and most detailed ever experimental data at 158 GeV. This contribution demonstrates the superior accuracy of the present dataset with respect to existing measurements. The comparison of p+p to Pb+Pb collisions shows a non-trivial system size dependence of the longitudinal evolution of hidden strangeness production, contrasting with that of other mesons. Furthermore, proton density fluctuations are investigated as a possible order parameter of the second order phase transition in the neighbourhood of the critical point (CP) of strongly interacting matter. An intermittency analysis is performed of the proton second scaled factorial moments in transverse momentum space. A previous analysis of this sort revealed significant power-law fluctuations for the “Si”+Si system at 158A GeV measured by the NA49 experiment. The fitted power-law exponent was consistent within errors with the theoretically expected critical value, a result suggesting a baryochemical potential in the vicinity of the CP of about 250MeV [24]. The analysis will now be extended to NA61/SHINE systems of similar size, Be+Be and Ar+Sc, at 150A GeV. Finally, spectator-induced electromagnetic (EM) effects on charged meson production are being studied and bring information on the space-time position of the pion formation zone, which appears to be much closer to the spectator system for faster pions than for slower ones. On that basis, we demonstrate that the longitudinal evolution of the system at CERN SPS energies may be interpreted as a pure consequence of local energymomentum conservation.

Intermittency Approach in the Nuclear Collisions of 28Si + AgBr at 14.6A GeV - Nuclear Emulsion Experiment a Particle Detector

A new method has been applied for the study of intermittency in the collisions of 28Si + AgBr at 14.6 A GeV for the produced relativistic charged particles by using the method of mixed factorial moment (MFM). In this paper an analysis has been made for the presence of fractal behavior with three different approaches of Scaled factorial Moments (SFMs) named as- horizontal, vertical and mixed (horizontal and vertical together). The non-statistical fluctuations of relativistic charged particles have been calculated on events with different degree of centrality. These results have been compared with the results of simulated data obtained from UrQMD model and we find a good agreement between experimental data and simulated data.

Intermittency Approach in the Nuclear Collisions of 28Si + AgBr at 14.6A GeV - Nuclear Emulsion Experiment a Particle Detector

A new method has been applied for the study of intermittency in the collisions of 28Si + AgBr at 14.6 A GeV for the produced relativistic charged particles by using the method of mixed factorial moment (MFM). In this paper an analysis has been made for the presence of fractal behavior with three different approaches of Scaled factorial Moments (SFMs) named as- horizontal, vertical and mixed (horizontal and vertical together). The non-statistical fluctuations of relativistic charged particles have been calculated on events with different degree of centrality. These results have been compared with the results of simulated data obtained from UrQMD model and we find a good agreement between experimental data and simulated data.

A study of event-by-event fluctuations in relativistic heavy-ion collisions

A method for selecting events with densely populated narrow regions or spikes in a given data sample is discussed. Applying this method to 200 A GeV/c 32 S - AgBr and 32 S -Gold collision data, a few events having "hot regions" are chosen for further analysis. The finding reveals that a systematic study of particle density fluctuations, if carried out in terms of scaled factorial moments, and the results are compared with those for the analysis of correlation free Monte Carlo events, would be useful in identifying events with large dynamical fluctuations. Formation of clusters or jet-like structure in multihadronic final states in the selected spiky events is also looked into and compared with the predictions of AMPT and independent emission hypothesis models by carrying out Monte Carlo simulation. The findings suggest that clustering or jet-like algorithm adopted in the present study may also serve as an important tool for triggering different classes of events.

DYNAMICS OF FRACTALITY AND PHASE TRANSITION IN MULTIPARTICLE PRODUCTION IN RELATIVISTIC NUCLEUS–NUCLEUS COLLISIONS

This paper reports the results of an investigation regarding occurrence of second-order phase transition in 14.5A GeV /c28 Si -nucleus interactions using the method of scaled factorial moments. Incidentally, the value of the universal scaling exponent, ν, for our experimental data is found to be 1.224±0.068, which is quite close to its critical value 1.304. An attempt is also made to search for the evidence of phase transition in terms of Levy index, μ, using scaled factorial moments as well as Takagi moments for both experimental and FRITIOF generated data sets. Average value of μ, calculated from Fq moments, turns out to be more than unity but is less than unity when estimated in terms of Takagi moments for both the data sets. Thus the analyses carried out in terms of Fq and Takagi moments reveal the occurrence of nonthermal and thermal phase transitions, respectively.

FRACTAL ANALYSIS OF FLUCTUATION IN THE EMISSION SPECTRUM OF TARGET-ASSOCIATED FAST PARTICLES

We study the intermittent and fractal behavior of the emission spectrum of target-associated fast particles from 84 Kr-AgBr interactions at 0.95 GeV/A. We used χ( cos θ) as the phase space variable. Normalized or scaled factorial moments studies for various orders of moment q = 2–5, confirmed the intermittent behavior. Gq moments have a fractal interpretation in their fluctuation in phase space. Our studies reveal the multi-fractal behavior of the emission spectrum.

INTERMITTENCY IN 4.5A AND 14.5A GeV/c28Si-NUCLEUS INTERACTIONS

The occurrence of intermittent patterns in 14.5 A GeV/c 28 Si -nucleus interactions is examined in terms of Scaled Factorial Moments (SFMs), introduced by Bialas and Peschanski. Further, to examine the dependence of various interesting characteristics of SFMs on incident energy, the data on 4.5 A GeV/c 28 Si -nucleus collisions available in our laboratory are analyzed. Interestingly, log-log plots between rapidity interval δη and the qth order factorial moment Fq for both the energies exhibit linear behavior indicating thereby the presence of intermittency in the interactions investigated. Moreover, to look at the fractal nature of the particle emitting sources, variation of the fractal dimensions, dq with the order of the moment is investigated. Finally, study of the variation of λq [=(ϕq+1)/q)] with the order of the moment, q indicates a possibility of non-thermal phase transition in certain types of events

EVIDENCE FOR INTERMITTENCY IN HADRON–NUCLEUS AND NUCLEUS–NUCLEUS COLLISIONS AT RELATIVISTIC ENERGIES

Scaled factorial moments are calculated for multiplicity distributions in the pseudorapidity intervals of secondary particles produced in p-Em collisions at 400 GeV, π-- Em collisions at 340 GeV and 12 C-Em collisions at 3.6 A GeV. In the p-Em and 12 C-Em collisions an intermittent power law growth of the factorial moments clearly observed, but no such dependence is found in π-- Em collisions. Higher order scaled factorial moments are found to obey a scaling law.