16O AgBr Interactions Research Articles

Chaos in multiparticle production in 16O–AgBr interactions at 60 A GeV and its target excitation dependence

Chaos in multiparticle production in 16O–AgBr interactions at 60 A GeV and its target excitation dependence

Study of multiplicity fluctuations in terms of strongly intensive quantity in forward-backward zone

A completely new study of forward-backward multiplicity fluctuation of produced pions in nuclear emulsion detector has been carried out by the method of strongly intensive quantity ΣFB for 16O-AgBr, 28Si-AgBr and 32S-AgBr interactions at 4.5 AGeV/c. Experimental analysis has been compared using MC-RAND events and UrQMD simulated events. UrQMD model could not reproduce the experimental results. Outcome of this analysis supports the presence of dynamical fluctuations in multiparticle production at 4.5 AGeV/c. The results on strongly intensive fluctuation measures at a lower energy show much larger fluctuations in comparison to the higher energy data studied so far.

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

A detailed study of event-by-event fluctuations of maximum particle density of the produced particles with respect to the width of the pseudo-rapidity interval in terms of the scaled variance ω has been carried out for 16O-AgBr, 28Si-AgBr and 32S-AgBr interactions at 4.5 A GeV/c. For all the interactions the values of scaled variance are found to be greater than one indicating the presence of strong event-by-event fluctuations of maximum particle density values in the multiparticle production process. The event-by-event fluctuations are found to decrease with the increase of the width of the pseudo-rapidity interval. Experimental analysis has been compared with the results obtained from the analysis of events simulated by generating random numbers (MC-RAND) and the Ultra-Relativistic Quantum Molecular Dynamics (UrQMD) model. MC-RAND events show significantly less event-by-event fluctuations in comparison to the experimental data. The UrQMD model also failed to reproduce the experimental results. Comparison of our analysis with the outcome of other analysed emulsion data has also been presented.

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

A detailed study of event-by-event maximum pseudo-rapidity gap fluctuations in relativistic heavy-ion collisions in terms of the scaled variance ω has been carried out for 16O-AgBr, 28Si-AgBr and 32S-AgBr interactions at an incident momentum of 4.5 AGeV/c applying the multiplicity cut (Ns > 10). For all the interactions the values of scaled variance are found to be greater than zero indicating the presence of strong fluctuation of maximum pseudo-rapidity 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 the Ultra Relativistic Quantum Molecular Dynamics (UrQMD) model. The UrQMD-model–simulated values of event-by-event fluctuations of the maximum pseudo-rapidity gap are less than the corresponding experimental values.

Chaotic Multiparticle Production in Ring and Jet Structured Events in Heavy Ion Interaction: A Study in Multidimensional Phase Space

Two different classes of events exist in case of 16O–AgBr interactions at 60 AGeV, namely, ring-like and jet-like structured events. We have performed a rigorous study on the erratic behaviour of produced particles in ring-like and jet-like events in 16O–AgBr interactions at 60 AGeV with the help of entropy index μq. We have analysed the data in two dimensional phase space. The data reveal different pionisation for ring-like and jet-like events.

Forward–backward multiplicity correlations in ring like and jet like events in 16O–AgBr interactions at 60 AGeV

We have studied the forward–backward correlations of charged-particle multiplicities in symmetric bins in pseudorapidity space in order to gain insight into the underlying correlations structure of particle production in case of ring-like and jet-like events of 16O–AgBr interactions at 60 AGeV. The variance σc2 of a suitably defined the forward-backward asymmetry variable C has been determined. The experimental results confirm correlations of the produced particles in the forward and the backward pseudorapidity region for both ring-like and jet-like events.

Multiplicity and entropy scaling of medium-energy protons emitted in relativistic heavy-ion collisions

The behavior and the properties of medium-energy protons with kinetic energies in the range 26 - 400 MeV is derived from measurements of the particle yields and spectra in the final state of relativistic heavy-ion collisions (16O-AgBr interactions at 60 A and 200 A GeV and 32S-AgBr interactions at 3.7 A and 200 A GeV) and their interpretation in terms of the higher order moments. The multiplicity distributions have been fitted well with the Gaussian distribution function. The data are also compared with the predictions of the modified FRITIOF model, showing that the FRITIOF model does not reproduce the trend and the magnitude of the data. Measurements of the ratio of the variance to the mean show that the production of target fragments at high energies cannot be considered as a statistically independent process. However, the deviation of each multiplicity distribution from a Poisson law provides evidence for correlations. The KNO scaling behavior of two types of scaling (Koba-Nielsen-Olesen (KNO) scaling and Hegyi scaling) functions in terms of the multiplicity distribution is investigated. A simplified universal function has been used in each scaling to display the experimental data. An examination of the relationship between the entropy, the average multiplicity, and the KNO function is performed. Entropy production and subsequent scaling in nucleus-nucleus collisions are carried out by analyzing the experimental data over a wide energy range (Dubna and SPS). Interestingly, the data points corresponding to various energies overlap and fall on a single curve, indicating the presence of a kind of entropy scaling.

Measurements of charged hadron fluctuations in pseudo-rapidity bins in 16O-AgBr at 60 A GeV and 32S-AgBr at 200 A GeV

We have measured the hadron-hadron correlation in the multiparticle production process of 16O-AgBr interactions at 60A GeV and 32S-AgBr interactions at 200A GeV in the forward and backward zone of the pseudo-rapidity space using the normalized factorial cumulant moment method. The experimental results have been compared with the Monte Carlo data generated according to the independent emission model. The results reveal that the observed correlation between the produced hadrons is purely dynamical. Correlation is found to be stronger in the backward zone than that in the forward zone of the pseudo-rapidity space for both interactions. Factorial cumulant moments for the experimental data show a power law rise with decreasing phase space bin size. The results obtained from the experimental data have also been compared with those obtained from analyzing FRITIOF data. Though FRITIOF data itself show the presence of a measured correlation among the hadrons, in most of the cases the values of the factorial cumulant moments are much less than the experimental values and they remain constant with phase space bin size. The study might hint towards the Bose-Einstein correlation as the origin of the observed behavior of the measured correlation. The failure of FRITIOF data to reproduce the exact experimental behavior in terms of factorial cumulant moment also supports this notion as the model does not take the BE correlation into account.

Fluctuation of fluctuations in pionisation: Target excitation dependence

This paper presents some interesting and informative results of experimental investigation on target excitation dependence of fluctuation of fluctuations studies on produced pions emitted in 16O-AgBr interactions at 60 AGeV and 32S-AgBr interactions at 200 AGeV. A search for the possible signature of chaotic behavior of multiparticle production in nucleus-nucleus collision has been performed with the help of entropy index, μq. To study the target excitation dependence of the chaotic behavior, the whole dataset is divided into subsamples having different number of recoil target protons which may be considered as a measure of target excitation.

Ring-Like and Jet-Like Events in Ultra High-Energy Interactions—an Analysis in Terms of Multifractal Parameters

Ring-like and jet-like events produced in 16O-AgBr interactions at 60 AGeV are analyzed in terms of multifractal G-moment method and factorial moment method in both η space and ϕ space for emitted pions. Further, the Levy indices and multifractal specific heat c have been calculated. The results clearly indicate that μ and c both are different in ring-like and jet-like events depicting different mechanism in the production process.

Genuine pion–pion correlations in heavy-ion collisions

The search for genuine two-particle dynamical correlations among the pions produced in 16O–AgBr interactions at 60 AGeV and 32S–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 16O–AgBr and 32S–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 (K2) against the number of bin M has been fitted with a function K2 = aMb 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.

Multiplicity dependence of entropy in different rapidity bins in high-energy nucleus–nucleus interactions

Multiplicity dependence of pionic entropy in different overlapping pseudo-rapidity bins has been investigated in 16O–AgBr interactions at 2.1 AGeV, 12C–AgBr and 24Mg–AgBr interactions at 4.5 AGeV, 16O–AgBr interactions at 60 AGeV and 32S–AgBr interactions at 200 AGeV. Entropy is found to increase with an increase of average multiplicity initially and is later observed to reach an approximate saturation for all the interactions. The experimental points have been fitted with a theoretical function S = a[1 - exp ( -b〈n〉 )] . The fitting seems to be better at lower energy. The obtained result has been compared with Monte Carlo simulated events for all the interactions. Experimental results obtained from 16O–AgBr interactions at 60 AGeV and from 32S–AgBr interactions at 200 AGeV have also been compared with the events generated by the Lund Monte Carlo code (the FRITIOF model).

Multiplicity scaling of target protons in high-energy nucleus–nucleus and hadron–nucleus interactions

Multiplicity scaling of target protons emitted from nucleus–nucleus (16O–AgBr interactions at 2.1 AGeV and 32S–AgBr interactions at 200 AGeV), pion–nucleus (π−–AgBr interactions at 350 GeV/c) and proton–nucleus interactions (p–AgBr interactions at 200 GeV/c) has been investigated. The experimental points are found to lie approximately on the curve described by ψ(z) = Azexp ( − Bz) with A = 3.36 ± 0.19 and B = 1.74 ± 0.06 for all the four interactions. A comparison of the fit with the function ψ(z) = (Az + Bz3 + Cz5 + Dz7)exp ( − Ez) has also been performed.

Multifractality in charged pion production at a few GeV/n

The multifractal analysis of charged pion produced in 16O–AgBr interactions at 2.1 AGeV and 24Mg–AgBr interactions at 4.5 AGeV has been investigated using the Takagi moment method in pseudo-rapidity space. The generalized fractal dimensions Dq are determined for these two interactions for different orders of moment. Experimental data reflects multifractal geometry in the multipion production process. From the knowledge of the generalized fractal dimensions Dq, the multifractal specific heat has also been evaluated for these data. A detailed comparison is presented with the results obtained from 12C–AgBr and 28Si–AgBr interactions at 4.5 AGeV/c, 28Si–AgBr interactions at 14.5 A GeV/c, 16O–AgBr interactions 60 AGeV and 32S–AgBr interactions 200 AGeV from the recent literatures.

Characteristics of multiplicity distribution of target fragments in forward and backward hemispheres in high-energy nucleus–nucleus interactions

A detailed study on the mechanism of the evaporation of target fragments in the forward and backward hemispheres in 12C–AgBr interactions at 4.5A GeV, 28Si–AgBr interactions at 14.5A GeV, 16O–AgBr interactions at 60A GeV and 32S–AgBr interactions at 200A GeV is carried out in terms of the multiplicity distribution. The nature of the multiplicity distribution in the forward and backward hemispheres is found to be different across all the interactions. The asymmetry parameters and the forward–backward ratios were also calculated for the above-mentioned interactions. The asymmetry parameters and the forward–backward ratios from other nucleus–nucleus interaction data were compared with our results. The forward–backward ratios of target fragments are found to be nearly the same for all the nucleus–nucleus interactions. The forward–backward ratios of all the interactions are greater than 1, suggesting that the probability of emission of fragments in the forward hemisphere is higher than that in the backward direction. The multiplicity moment, entropy and reduced entropy, i.e. the ratio of entropy to average multiplicity of target fragments, are evaluated in both the forward and backward hemispheres for all the four above-mentioned interactions. The values of multiplicity moments are found to be energy independent up to 60A GeV energy in the backward hemisphere. The reduced entropy is also found to be almost energy independent to within experimental error in the backward hemisphere. No such observation can be made in the forward hemisphere. The total entropy of the target fragments is found to be higher in the forward hemisphere. A study of correlation in terms of the scaled variance was also carried out in both the hemispheres for all the nucleus–nucleus interactions. No systematic variation of correlation either with energy or with the size of the projectile nucleus has been noticed. The study yields quite interesting information on the mechanism of particle evaporation in the backward hemisphere.

Takagi multifractal moment and Levy index analysis of target residues at SPS energies

This work presents the analysis about multifractality using the concept of T q moment and Levy index using the data of target residues emitted from 16O–AgBr (at 60 AGeV) interaction beams. The analysis has been performed for full phase space as well as for forward and backward hemispheres. The analysis shows difference in degree of multifractality in the three cases (full, forward and backward) of 16O–AgBr interactions at 60 AGeV.

Pion fluctuation and its multiplicity dependence in ultrarelativistic nuclear collisions

This paper studies the multiplicity dependence of the fluctuation pattern of pions produced for 16O–AgBr interactions at 60 A GeV and 32S–AgBr interactions at 200 A GeV. We divided the data for the pions produced into four sets depending on the number of shower tracks (ns). We investigated the fluctuation pattern of emitted pions corresponding to different sets in both η (pseudorapidity) and ϕ (azimuthal angle) space. The multiplicity dependence was studied with respect to parameters αq, Dq, multifractal specific heat c, and effective fluctuation strength αeff. The study clearly indicates that the fluctuation pattern depends on multiplicity both in pseudorapidity and azimuthal angle space for 16O initiated interactions. However, for 32S initiated interactions, no multiplicity dependence is evidenced by the data in azimuthal angle space. For both, the multiplicity dependence is not very strong and significant only at large average multiplicity. Multiplicity dependence was further studied in a small window around the central pseudorapidity, and we found that multiplicity dependence is more prominent in the central region. The multiplicity dependence of αeff is more pronounced in the case of 32S–AgBr interactions than in case of 16O–AgBr interactions. PACS Nos.: 25.75–q, 24.60 Ky

Intermittent type fluctuation of target fragments produced in 16O-AgBr interactions at 4.5 AGeV/c**Supported by National Natural Science Foundation of China (10675077, 10475054), Shanxi Provincial Natural Science Foundation (2007011005) and Shanxi Provincial Science Foundation for Youths (20051002)

A study of intermittency of target associated fragments produced in the interactions of 16OAgBr at 4.5 AGeV/c with nuclear emulsion using the method of factorial moments, Fq, has been performed. The dependence of the moments on the number of bins M is found to follow a power law behavior for the experimental data in terms of new scaled variable χ(z) suggested by Bialas and Gazdzicki. The anomalous dimensions, dq, increase linearly with the order of moments, q. This observation indicates the association of multifractility with production mechanism of target associated fragments.

Intermittent behavior of fast and slow target fragments from 16O–AgBr interactions at 3.7 A GeV

Angular distributions of fast and slow target particles produced in 16O–AgBr interaction at 3.7 A GeV have been reported. Intermittency and fractal behavior have been studied for emission spectra of target associated fast and slow particles. Intermittent behavior is observed for both knocked out and slow target fragments. In both the cases anomalous dimensions are seen to increase with the order of moments thereby indicating the association of multifractility with production mechanism of both fast and slow target associated particles.

Evidence of self-similar target fragmentation process in 16O–AgBr interactions at 3.7 A GeV

Self-affine multiplicity scaling is investigated in the framework of two-dimensional factorial moment methodology using the concept of Hurst exponent ( H ) . Investigation of the experimental data of target fragments emitted in 16O–AgBr interactions at 3.7 A GeV revealed that best power law behavior is exhibited at H = 1 indicating self-similar multiplicity fluctuations.