S. Mookerjee

Scaling properties of charged particle multiplicity distributions in oxygen induced emulsion interactions at 14.6, 60 and 200 A GeV

Abstract The multiplicity distributions of shower particles (ns) are measured in inclusive inelastic oxygen emulsion interactions. Scaling is observed in the normalized variable ns/〈ns〉 for 14.6, 60 and 200 AGeV. The dependence of 〈ns〉 on the charge flow in the forward direction (QZD) and the distribution of the number of participating projectile protons is examined. The normalized multiplicities as a function of QZD seem also to be independent of incident energies. A comparison with the Lund model Fritiof yields satisfactory agreement.

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.

Multiplicities and rapidity densities in 200 A GeV 16O interactions with emulsion nuclei

Abstract We report on an experiment in which emulsion chambers were exposed to a beam of 200 A GeV 16 O at the CERN SPS. Pseudo-rapidity distributions are measured with high precision. Pseudo-rapidity densities of 140 particles per unit rapidity corresponding to an energy density of about 3 GeV/fm3 are observed. Pseudo-rapidity density distributions and fluctuations are found to satisfactorily agree with the Lund Monte Carlo model Fritiof, although new and unknown sources for fluctuations might still be present.

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.

Azimuthal anisotropy in S + Au reactions at 200 A GeV

Abstract Azimuthal correlations of photons produced at mid-rapidity in 200 A GeV S + Au collisions have been studied using a preshower photon multiplicity detector in the WA93 experiment. The Fourier expansion method has been employd to estimate the event plane via the anisotropy of the event as a function of centrality. The event plane correlation technique has been used to determine the true event anisotropy, beyond the anisotropy which arises due to finite multiplicity. The VENUS event generator with rescattering and proper simulation of the detector response can explain only a portion of the observed anisotropy. The residual anisotropy is found to be of the order of 5% for semi-central collisions. This suggests that directed collective flow of the produced particles is present at SPS energies.

A search for non-statistical particle density fluctuations in 16O + Ag(Br) and 32S + Au interactions at 200 A GeV

Abstract Fluctuations in particle densities of non-statistical origin are studied in central 16 O+Ag(Br) and 32 S+Au interactions at 200 A GeV. Non-statistical fluctuations in the 32 S-induced interactions seem to enhance the local particle densities, and suggest the presence of intermittancy. The fluctuations are found to be accompanied by a clustering tendency also in the azimuthal plane. A new method for the study of azimuthal correlations is proposed.

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.

Target nucleus fragmentation in 16O+(Ag,Br) interactions at 200 A GeV

Abstract The multiplicity distributions of low-energetic target-associated particles from 200 A GeV oxygen-induced interactions with emulsion nuclei are presented. The experimental distributions are compared with distributions obtained using the Ranft and Fritiof simulation codes. It is found that the intra-nuclear cascade plays an important role in ion-induced interactions, similar to what is the case for hadron-induced interactions.

On the multiplicity fluctuations in relativistic heavy ion collisions

Abstract In the present letter we discuss the general features of the multiplicity distributions in relativistic heavy ion collisions. It is shown that from simple statistical considerations it is possible to predict the dependence of the dispersions of multiplicity distributions on the average multiplicities in any given rapidty wwindow. The applicability of the negative binomial distribution to multiplicity distributions from collisions with heavy ions is discussed.

ON THE ENERGY AND MASS DEPENDENCE OF THE MULTIPLICITY IN RELATIVISTIC HEAVY-ION INTERACTIONS

The average multiplicities of singly charged relativistic particles in oxygen-induced interactions with a nuclear emulsion target are studied over the energy range 2.1–200 A GeV. A similar energy dependence as for proton-induced interactions is observed. Both the number of participating nucleons and the number of binary collisions are shown to be of importance for the particle production.