AgBr Interactions Research Articles

VOID ANALYSIS OF TARGET RESIDUES AT SPS ENERGY

This paper presents new data on void analysis of target residues in ultrarelativistic nucleus–nucleus interaction. The study reveals a set of interesting observations. Void probability shows a scaling behavior at high energy (32 S –AgBr interactions at 200 A GeV) in both forward and backward hemisphere. Whereas such behavior is absent at low energy (16 O –AgBr interactions at 60 A GeV) in backward hemisphere.

LÉVY INDEX AND MULTIFRACTAL CHARACTERISTICS OF RING-LIKE AND JET-LIKE EVENTS IN HIGH ENERGY NUCLEAR COLLISIONS

We perform a Lévy index analysis of relativistic shower particles produced in the interactions of 32 S nuclei at 200A GeV with nuclear emulsion using the results of factorial moment Fq in two-dimensional anisotropic (η - ϕ) space. We carry out the same investigation for target fragments produced in 32 S - AgBr interactions at 200A GeV energy for both events in emission angle space and azimuthal angle space. The analysis reveals that for pions the value of Lévy index μ is 1.491 ± 0.025 for ring-like events and μ ~ 2.004 ± 0.054 for jet-like events which indicates different degree of multifractality. In case of target fragments jet-like events show a value of μ ~ 1.871 ± 0.010 whereas ring-like events yields an unphysical value (μ > 2) the implication of which need to be explored.

Pionization at AGS and SPS energies ― degree of coherence and its target excitation dependence

The target excitation dependence of the higher order cumulant correlation of pions is studied in the present work in the framework of void probability scaling. The data set of pions produced for16O–AgBr interactions at 2.1 AGeV and32S–AgBr interactions at 200 AGeV was divided into three sets depending upon the number of grey tracks ng. The different sets of ngcorrespond to different degrees of target excitation. Analysis was carried out for each set in different pseudorapidity intervals. For the lower projectile energy the void probability scaling is observed only for low target excitation for all pseudorapidity intervals. For the comparatively higher projectile energy, scaling is observed for all pseudorapidity intervals and all target excitation. In other words, for higher projectile energy, scaling is almost independent of the target excitation. The results are interpreted from the point of view of the two source model of particle production.

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.

Evidence of self-affine multiplicity fluctuation of particle production in 84Kr–emulsion interactions at 1.7 A GeV

Self-affine multiplicity fluctuation is investigated by using the two-dimensional factorial moment methodology and the concept of the Hurst exponent (H). Investigation on the experimental data of compound particles and target fragments emitted in 84Kr–AgBr interactions at 1.7 A GeV reveals that the best power law behaviours are exhibited at H = 0.7 and 0.6 respectively, and the data for shower particles produced in 84Kr-emulsion interactions at 1.7 A GeV indicate that the best power law behaviour occurs at H = 0.6, all of which show the self-affine multiplicity fluctuation patterns. The multifractality and the non-thermal phase transition occurring during producing the compound particles, the target fragments, and the shower particles in the 84Kr–AgBr interaction and the 84Kr–emulsion interaction are also discussed. The multifractality is observed during producing compound particles, target fragments, and shower particles. In the target fragment production, an evidence of non-thermal phase transition is observed, but in the shower particle production and the compound particle production, no evidence of non-thermal phase transition is observed.

Target excitation dependence of the entropy index in 350 GeV/c π−–AgBr collisions

In this paper a detailed study on the erratic behaviour of multiparticle production in π−–AgBr interactions at 350 GeV has been performed with the help of the parameter ‘entropy index’ μq, which is a measure of chaotic behaviour in multipion production processes. This index describes the event-to-event fluctuation of factorial moments which measures the spatial fluctuation of multiplicity distribution. The analysis reveals a large value for the entropy index, signifying the chaotic behaviour of the produced pions in high-energy hadron–nucleus interactions. It has been observed that the multipion production process becomes less chaotic with an increasing average multiplicity of the final states. The study has further been extended to know the target excitation dependence of chaoticity of pions; a positive dependence is indicated by the data.

Spikes in ring-type events from ultra relativistic nuclear collisions

This paper reports the observation of some peculiar ring-like events in ultra relativistic nuclear interactions (the 32S–AgBr interaction at 200 A GeV and the 16O–AgBr interaction at 60 A GeV). These events have been analysed in the light of Čerenkov gluon radiation as proposed by Dremin. Also the value of the refractive index of the nuclear matter is calculated. The analysis shows values of refractive index different from that revealed in normal nuclear matter. PACS Nos.: 25.75.–q, 24.60.Ky, 12.40.Ee

MULTIFRAGMENTATIONS OF TARGETS AT SPS ENERGY — EVIDENCE OF BOTH MONOFRACTALITY AND MULTIFRACTALITY

This paper reports the fractal analysis of target residues in both ring- and jet-like events emitted from 32 S - AgBr interactions at 200 AGeV using Takagi's prescription. The study reveals a very interesting feature of emission process such as monofractality of target fragments in jet-like events and multifractality of target fragments in case of ring-like events.

Variation of mean multiplicity of intermediate mass fragments with the bound charge of the fragmenting system-deviation from the universal behaviour

In this work an attempt has been made to study the variation of normalized mean multiplicity with the normalized Zb for 0.95A GeV 84Kr — Em and 84Kr — AgBr interactions Though the data points of the present investigation exhibit the same pattern of the universal curve of ALADIN group, the maximum value of < NIMF > of the present investigation is found to be about 17 times larger than that of the universal curve.

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

Variation of mean multiplicity of intermediate mass fragments with the bound charge of the fragmenting system-deviation from the universal behaviour

In this work an attempt has been made to study the variation of normalized mean multiplicity with the normalized Zb for 0.95A GeV 84Kr — Em and 84Kr — AgBr interactions Though the data points of the present investigation exhibit the same pattern of the universal curve of ALADIN group, the maximum value of < NIMF > of the present investigation is found to be about 17 times larger than that of the universal curve.

Evidence of intermittent fluctuation of target residue in 84Kr–AgBr interactions at 1.7 A GeV

Intermittency and fractal behavior have been studied for emission spectra of target associated fragments from 84Kr–AgBr interactions at 1.7 A GeV in emission angle space and azimuthal angle space separately. Intermittent behavior is observed for both spaces. From the intermittency exponent, the anomalous fractal dimension d q is calculated and the variation of d q with the order q is investigated. It is found that the anomalous dimensions increase with the order of moments q thereby indicating 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.

Higher order correlation of the pions and their target excitation dependence in relativistic and ultrarelativistic nuclear collisions

The target excitation dependence of higher order correlation of the pions is investigated in the present work using the data of 16O–AgBr interactions at 2.1 and 60 A GeV and 32S–AgBr interactions at 200 A GeV. The data are divided into different sets of ng which correspond to different degrees of the target excitation. The target excitation dependence was evident at the lower projectile energy—at the higher projectile energy no target excitation dependence was revealed by the data.

Intermittency of Target Fragments in 16O–AgBr Collisionsat 4.5 A GeV/c

We report the angular distributions of grey and black particlesproduced in 16O–AgBr interactions at 4.5 A GeV/c in nuclearemulsion. Intermittency and fractal behaviour are studied for emissionspectra of target associated grey and black particles. Intermittentbehaviour is observed for both grey and black particles. In both thecases, anomalous dimensions are seen to increase linearly with theorder of moments, thereby indicating the association of multifractilitywith production mechanism of both grey and black particles.

Chaos analysis of nuclear fragments in high energy collisions

This paper deals with fixed target AGS and SPS data of beam energies 14.5 and 200 A GeV respectively. A detailed study on chaos in the nuclear fragmentation process of 28Si–AgBr interactions at 14.5 A GeV and 32S–AgBr interactions at 200 A GeV has been performed using a new parameter, the entropy index. The analysis provides new data on the evidence of the erratic behavior of the target fragments signifying chaotic target fragmentation and also quantify the measure for chaos in high and ultra-high energy heavy-ion interactions. Further, it is also observed that the target fragmentation process becomes less chaotic with the increase of average multiplicities of the final states.

ENERGY DEPENDENCE OF MULTIDIMENSIONAL FRACTAL BEHAVIOR OF PIONS IN NUCLEAR COLLISION

This paper reports a study on multidimensional fractal behavior of pions emitted in 16 O - AgBr interactions at 2.1 and 60 AGeV by dividing the full bin range into different sub-bin ranges. Analysis is performed in (Xη - Xϕ) space following two-dimensional factorial moment methodology using the concept of Hurst exponent, which takes into account the anisotropy of phase space. Different scaling behavior is observed in different bins at two different energies. The data show a positive evidence of change of fluctuation pattern from self-similarity to self-affinity with increase of energy. Multifractal dimensions have been calculated in each case and it is observed that pions at both energies exhibit multifractal behavior.

Evidence of intermittent fluctuation of target fragments in 84 Kr–AgBr interactions at 1.7 A GeV

Intermittency and fractal behaviour have been studied of emission spectra of target associated fragments from 84Kr–AgBr interactions at 1.7A GeV in emission angle space and azimuthal angle space separately. The intermittent behaviour is observed in the two spaces separately. From the intermittency exponent, the anomalous fractal dimension dq is calculated and the variation of dq with the order q is investigated. It is found that the anomalous dimensions are found to increase with the order of moments q, thereby indicating the relation of multifractality to production mechanism of target associated fragments.

Evidence of self-affine multiplicity scaling of charged-particle multiplicity distribution in hadron-nucleus interaction

A self-affine analysis of charged-particle multiplicity distribution (protons + pions) in π −-AgBr interaction at 350 GeV/c is performed according to the two-dimensional factorial moment methodology using the concept of Hurst exponent in X cosθ -X ϕ phase space. Comparing with the results obtained from self-similar analysis, the self-affine analysis shows a better power-law behaviour. Corresponding results are compared with shower multiplicity distribution (pions). Multifractal behaviour is observed for both types of distributions.