N. Ahmad

Erraticity behaviour in relativistic nucleus–nucleus collisions

Event-by-event fluctuations in factorial moments in terms of erraticity measures are examined by analysing the experimental data on 4.5 A and 14.5 A GeV/c 28Si–nucleus interactions. The findings are compared with the predictions of the Lund Monte Carlo model, FRITIOF. It is observed that the magnitudes of erraticity moments decrease with increasing multiplicity and are essentially insensitive to the incident energy and mass of the beam/target nuclei. Furthermore, analysis of the correlation free Monte Carlo events clearly indicates that the erratic fluctuations arise mostly due to statistical reasons, particularly in the case of low multiplicity events.

Maximum Charged Particle Density Fluctuations in Relativistic Heavy-Ion Collisions

Correlation and clusterization amongst relativistic charged particles produced in 4.5 A and 14.5 Axa0GeV/c 28 Si–nucleus collisions are investigated by examining the maximum fluctuations in the densi...

CLUSTER PRODUCTION IN 14.5A GeV/c Si-NUCLEUS COLLISIONS

Characteristics of clusters of relativistic charged secondaries produced in 14.5A GeV/c Si-nucleus collisions are investigated by examining the behaviour of the rapidity gap distribution. The findings reveal that the maximum number of relativistic charged particles constituting a cluster is four. Further, the size of the cluster is observed to remain essentially independent of the mass of the struck nucleus. A comparison of the result of the present study with those reported earlier for hadron-hadron and hadron-nucleus collisions indicates that similar mechanisms may operate in the production of secondary particles in both hadronic and nuclear collisions at high energies.

Erratic fluctuations in 14.5A GeV/c 28Si−AgBr Collisions

Analysis of multiparticle production data on 14.5A GeV/c 28Si−AgBr collisions in terms of erraticity is carried out and the results are compared with those obtained from the Monte Carlo simulated data (using event generator HIJING). It is shown that like the multifractal spectrum through Gqmoments, erraticity spectrum may also be constructed from the observed power-law behaviour of the erraticity moments. Further, for examining the dominance of statistical fluctuations over the erraticity behaviour, correlation-free Monte Carlo events are simulated and analyzed. A comparison of the experimental and simulation results indicates that the fluctuations observed in the case of experimental data are not only because of the statistical reasons, but may have some dynamical origin.

EVIDENCE OF ENTROPY SCALING IN RELATIVISTIC NUCLEUS–NUCLEUS COLLISIONS

Significance of entropy, S, for explaining multiparticle production phenomenon in high energy nucleus–nucleus collisions is highlighted. For this, experimental data on 4.5A and 14.5A GeV/c 28Si-nucleus interactions are analyzed. An attempt is also made to explain the phenomenon using HIJING simulated interactions. Entropy is calculated for different classes of interactions. The plots of against for different categories of interactions reveal scaling behavior.

A COMPARATIVE STUDY OF THE EXPERIMENTAL AND SIMULATED VALUES OF MULTIFRACTAL SPECIFIC HEAT IN 14.5A GeV/c HEAVY-ION COLLISION

An attempt is made to study multifractal specific heat from Fq, modified Gq and Takagi moments, which can provide some interesting information about event-by-event fluctuations in heavy-ion collisions at high energies. It is an established fact that constancy of the specific heat (CSH) of solids and gases helps explain thermodynamical behavior of intermittency and multifractality in A–A collisions at different projectile energies. It is worthmentioning that the present paper deals with multifractal specific heat, c, extracted from Fq, modified Gq and Takagi moments for the experimental as well as FRITIOF generated data on 14.5A GeV/c28Si-nucleus interactions. The results obtained using the three approaches are compared for both the data sets. The observed power law behavior reflects self-similar property of the multiparticle production process. The common feature of the multifractal specific heat obtained using the three approaches is that there is no systematic variation in its value for different orders of the moments. Furthermore, the value of c is found to be different for both the data sets and no strong target mass dependence is observed in any of the cases. A noteworthy observation is that a non-zero finite value of the multifractal specific heat may be considered a good signal for the presence of multifractality in the relativistic charged particle multiplicity distribution.

EMISSION OF RELATIVISTIC HADRONS IN THE BACKWARD HEMISPHERE IN NUCLEAR COLLISIONS

The behavior of the relativistic charged particle multiplicities and the pseudorapidity distributions for 4.5A and 14.5A GeV/c28Si-nucleus interactions are investigated in terms of the number of emitted relativistic hadrons in the backward hemisphere, (relativistic charged particles emitted with space angle θs such that θs lies in the interval 90°≤θs≤270°). The η distribution of relativistic charged particles for the interactions with are found to be quite nicely fitted by a single Gaussian distribution (GD), while it is fitted by two distinct GDs when the interactions are not accompanied by backward relativistic hadrons. This, in turn, suggests that in the production of events having probably two different mechanisms operate.

Evidence of deconfinement phase transition in multiparticle production in relativistic nuclear collisions

This paper presents the results of an investigation pertaining to multifractal structure, degree of multifractality and occurrence of deconfinement phase transition. These results are obtained by carrying out analysis of generalized dimensions and Levy index involving relativistic charged particles produced on 14.5A GeV/c28Si-nucleus collisions following Takagis approach. The values of Levy index, μ, generalized fractal dimensions, Dq and degree of multifractality, βq, for different orders of moments are calculated in terms of Takagi moments for the experimental, FRITIOF, HIJING and random Monte Carlo (MC-RAND) generated events. The values of multifractal specific heats for all the above data sets are extracted using generalized dimensions, Dq. The analysis also shows small variations in the degree of multifractality for the experimental, FRITIOF and HIJING simulated events. However, the degree of multifractality is quite larger for the random Monte Carlo 28Si-nucleus generated events at 14.5A GeV/c. Furthermore, the analyses of multifractal specific heat and Levy index in terms of Takagi moments support the presence of multifractality and occurrence of deconfinement phase transition in the experimental and simulated data sets, but for the uncorrelated Monte Carlo simulated events, occurrence of nonthermal phase transition is revealed.

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/c28Si-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.

ANALYSIS BEYOND INTERMITTENCY IN MULTIPARTICLE PRODUCTION IN RELATIVISTIC NUCLEAR COLLISIONS

Possibility of occurrence of chaotic behavior in multiparticle production in relativistic nuclear collisions is examined. Erraticity spectrum and entropy index are determined and compared with those of FRITIOF-generated events. The results obtained in the present study reveal existence of erraticity in multiparticle production in relativistic nuclear collisions.