A detailed study of clan model parameters and their target dependence has been carried out in the light of void probability scaling for heavy (AgBr) and light (CNO) groups of targets present in the nuclear emulsion using 22 Ne (at an incident momentum of 4.1 GeV/c), 28 Si (at an incident momentum of 4.5 GeV/c), 16 O (at an incident momentum of 4.5 GeV/c) and 32 S (at an incident momentum of 4.5 GeV/c) projectiles. The variation of scaled rapgap probability with the single moment combination has been studied for all of the interactions. The experimental points are found to lie approximately on the NBD curve for all of the interactions, indicating a scaling behavior. According to the two-source model of particle production, in the case of 32 S-AgBr interactions at 4.5 GeV/c, the pion production mechanism has been found to be almost chaotic. On the contrary, for all of the other interactions at 4.1-4.5 GeV/c, pion production is predominantly chaotic. Average clan multiplicities (N) for all of the interactions are found to increase with the increase in the pseudo-rapidity interval η. The values of N for the AgBr target are larger than those for the CNO target. The average number of particles per clan (n c ) increases initially with the increase in pseudo-rapidity interval. An approximate saturation of the values of n c is observed for 22 Ne and 16 O projectiles around η = 6. With the increase in projectile size, the saturation of n c seems to be wiped out. It can also be observed from the tables that for a particular target the average number of particles per clan (n c ) increases with the increase in the size of the projectile nucleus. A comparison with the results of the SPS data has also been presented.

A study of rapidity gap probability has been carried out in 16 O-AgBr interactions at 2.1A GeV. The study reveals scaling behavior of the void probability. This analysis also confirms the validity of the linked-pair approximation for the N-particle cumulant correlation functions in the low energy regime.

We have presented a systematic study of two-particle rapidity correlations in terms of investigating the dynamical fluctuation observable σ 2 c in the forwardbackward pseudo-rapidity windows by analyzing the experimental data of 16 O-AgBr interactions at 4.5 AGeV/c, 22 Ne-AgBr interactions at 4.1 AGeV/c, 28 Si-AgBr and 32 S-AgBr interactions at 4.5 AGeV/c. The experimental results have been compared with the results obtained from the analysis of event sample simulated (MC-RAND) by generating random numbers and also with the analysis of events generated by the UrQMD and AMPT model. Our study confirms the presence of strong short-range correlations among the produced particles in the forward and the backward pseudo-rapidity region. The analysis of the simple Monte Carlo-simulated (MC-RAND) events signifies that the observed correlations are not due to mere statistics only; explanation of such correlations can be attributed to the presence of dynamical fluctuations during the production of charged pions. Comparisons of the experimental results with the results obtained from analyzing the UrQMD data sample indicate that the UrQMD model cannot reproduce the experimental findings. The AMPT model also cannot explain the experimental results satisfactorily. Comparisons of our experimental results with the results obtained from the analysis of higher energy emulsion data and with the results of the RHIC data have also been presented.

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The search for genuine two-particle dynamical correlations among the pions produced in 16 O-AgBr interactions at 60 AGeV and 32 S-AgBr interactions at 200 AGeV (super proton synchrotron data) has been carried out by the method of normalized factorial cumulant moments in pseudo-rapidity (η), azimuthal angle (φ) and two-dimensional anisotropic (η-φ) phase space. The analysis reveals the presence of genuine two-particle dynamical correlations among the pions in 16 O-AgBr and 32 S-AgBr interactions in both one and two dimensions. Stronger correlation has been observed in higher dimensional space. Correlations between the pions are found to decrease with the increase of projectile mass and energy. Experimental results have been compared with the FRITIOF data sample in the pseudo-rapidity space. In azimuthal angle space, events simulated by generating random numbers (Monte Carlo Simulation) have been used for the purpose of comparison. The FRITIOF data and the data of the simulated interactions have failed to reproduce the experimental results. The experimental results have also been compared with the event sample generated by the UrQMD model in both pseudo-rapidity and azimuthal angle space. Like the FRITIOF model, the UrQMD model is also unable to replicate the experimental results. The variation of normalized cumulant moment (K 2 ) against the number of bin M has been fitted with a function K 2 = aM b in both one and two dimensions. No fitting of this kind has been possible in the case of the FRITIOF data, UrQMD data and the MC simulated data. * This work is financially supported by University Grants Commision, Govt. of India (Sanction No PSW-044/11-12).