V.I. Bubnov

Rapidity densities and their fluctuations in central 200 A GeV 32S interactions with Au and Ag, Br nuclei EMU01 collaboration

The pseudo-rapidity density distributions of shower particles (n s ) are measured in central inelastic S + Au and S + Ag,Br inter-actions. The extracted maximum energy densities, while being higher for Au than for Ag.Br interactions, were found to be similar to those obtained for oxygen emulsion interactions. The correlation between rapidity density and shower particle multiplicity shows a small deviation from the Lund Model Fritiof for the highest energy densities in S + Au interactions, whereas the bulk of the data yields satisfactory agreement.

On intermittency in heavy-ion collisions and the importance of γ-conversion in a multi-dimensional intermittency analysis

Non-statistical fluctuations are used to probe the dynamical behaviour of multi-particle production in heavy-ion interactions at ultra-relativistic energies. In a one-dimensional analysis a 1〈ϱ〉-scaling is established and it is furthermore found that effects from higher-order particle correlations are small. In a two-dimensional analysis it is shown that a small background of particle pairs with a narrow opening angle can distort the observed signal. As an example we estimate the influence of γ-conversion and find that in our experiment γ-conversion alone gives results consistent with the experimental observations from a two-dimensional analysis. Whereas a two-dimensional analysis filters events where two particles are extremely close in phase space, the one-dimensional analysis picks out events with particles clustered in pseudorapidity, which are at the same time diluted in the azimuthal plane.

Energy, target, projectile and multiplicity dependences of intermittency behaviour in high energy O(Si,S) induced interactions

Fluctuations of charged particles in high energy oxygen, silicon and sulphur induced interactions are investigated with the method of scaled factorial moments. It is found that for decreasing bin size down to δη∼0.1 the EMU01 data exhibits intermittent behaviour. The intermittency indexes are found to decrease with increasing incident energy and multiplicity and to increase with increasing target mass. It seems also to increase as the projectile mass increases.

Nucleus nucleus collision as superposition of nucleon nucleus collisions

Abstract Angular distributions of charged particles produced in 16O and 32S collisions with nuclear track emulsion were studied at momenta 4.5 and 200 A GeV/c. Comparison with the angular distributions of charged particles produced in proton-nucleus collisions at the same momentum allows to draw the conclusion, that the angular distributions in nucleus-nucleus collisions can be seen as superposition of the angular distributions in nucleon-nucleus collisions taken at the same impact parameter bNA, that is mean impact parameter between the participating projectile nucleons and the center of the target nucleus

Review of recent results on particle production from EMU01

Abstract The EMU01 Collaboration has employed emulsion chamber and pellicle detectors to accumulate a large database of heavy nucleus interactions. Samples include both minimum bias and central collisions, analyzed in a uniform manner to extract multiplicities and angular distributions of charged particles and nuclear fragments. We find that the main features of these distribution are well represented by geometrical superposition models. A unique feature of EMU01 is the use of emulsion chambers with thin foil targets to observe produced particle angular distributions with exceptionally high precision, permitting extension of fluctuations and correlations analyses beyond the resolution limits imposed by other experimental techniques. The data are generally well reproduced by interaction simulations such as FRITIOF (the Lund monte carlo for nuclear collisons) which include only conventional physics effects. However, the analysis of fluctuations and correlations via factorial moment and cumulant techniques yields some suggestive results which require further investigation, both by continued analysis of existing data and from Au and Pb beam exposures scheduled for the next few years.

A systematic study of the energy independent behaviour of the fragmentation regions in16O-Em interactions from 3.7 to 200A GeV

The scaling behaviour in the fragmentation regions is investigated for16O-Em interactions from 3.7 to 200A GeV. It is found that in both the projectile- and the target-fragmentation regions, the multiplicity and pseudo-rapidity distributions as well as the two-particle pseudo-rapidity correlations are independent of incident energy. The intermittency indices at 14.6, 60 and 200A GeV are the same within the experimental errors, indicating that the limiting fragmentation hypothesis works with regard to dynamical as well as statistical fluctuations.