M. El-Nadi

Fragmentation of 28Si nuclei in nuclear emulsion

Topology of 28Si fragmentation at 14.6 A GeV in emulsion nuclei is given. In all events, the charge of each projectile fragment is measured. We report the measurements on total and some partial reactions cross sections of 28Si interactions. The data for Z6 can be qualitatively described by a statistical percolation model. The results are discussed and compared with those obtained from 28Si at 3.7 A GeV and 32S at 200 A GeV.

Multiple fast helium fragments production from 28Si-emulsion interaction at 14.6 A GeV

The measurements of partial production cross-sections of the multiple helium fragments emitted at 14.6 A GeV 28Si–emulsion interactions are reported. The production rate of helium fragments due to fragmentation of 28Si ions is studied and compared with that obtained from different projectiles at various energies. The dependence of Nα on the mass number of the incident beams is formulated. The multiplicity distributions of the helium fragments produced in 14.6 A GeV and 3.7 A GeV 28Si aswell as 200 A GeV 32S exhibit KNO scaling. The characteristics of He-multiplicity events associated with and without projectile fragments of charge Z ≥ 3 are investigated.

Nuclear multifragmentation of and in emulsion nuclei

The fragmentation of (3.7 A GeV) and (14.6 A GeV) is investigated as a function of the degree of disintegration of different components of photoemulsion nuclei. The experimental measurements show nearly energy-independent behaviour throughout the studied charge, size and multiplicity distributions of fragments produced from the two projectile beams. The various stages of the interactions, from the initial impact through to the final formation of clusters, are theoretically treated as follows. (i) The first stage of the interaction is modelled by the Glauber approach, using Reggeon parametrization for the nucleon-nucleon scattering amplitude. (ii) The additional inelastic interaction of secondary particles, produced in the primary stage, with other nucleons of the nucleus is analysed in the framework of a Reggeon-theory inspired model. (iii) The phenomenological percolation-evaporation model is used to describe the spectator part of the nucleus.

Target-Associated Particles Production in the Interactions of 3.7 and 200A GeV Sulphur Projectiles with Nuclear Emulsion

The characteristics of the associated particles produced in 3.7 and 200A GeV 32S-emulsion inelastic interactions are reported. The experimental data at 3.7 A GeV are compared with the predictions of the standard cascading evaporation model. For explaining the results at higher energy (200A GeV), a simple model which includes the nucleon sub-structure (Reggeon model) is introduced. This model is found to be capable of producing the mean features of the data obtained for the two used exposures.

Sulphur dissociation in nuclear emulsion at 3.7 and 200A GeV

In this work, the electromagnetic dissociation (EMD) of sulphur projectile induced by two widely differing energies in nuclear emulsions is investigated. Although the percentages of EMD events of the total numbers of studied interactions are relatively small, i.e. 5.7 and 14.4% for 3.7 and 200A GeV interactions respectively, one could extract some results out of them. The emission of a proton through the 32S(γ, p)31P channel is found to be a dominant process (43.8%) at 200A GeV whereas the single alpha emission through the 32S(γ, α)28Si channel is the dominant one (34.0%) at 3.7A GeV. Multiplicity distributions of hydrogen and helium isotopes as well as the measured probabilities for the different modes of fragmentation are studied. The comparison of the present results, from electromagnetic and peripheral nuclear interactions, indicates the effective role of the different reaction mechanisms at ultra-relativistic energy (200A GeV). The experimental inclusive cross sections of different fragmentation modes produced in the EMD of 32S ions at 200A GeV were found to be in satisfactory agreement with the predictions of the combined approach of Pshenichnov et al.

Nuclear temperature and multiplicities of relativistic he fragments from16O-emulsion interactions at 200A GeV

SummaryThis work mainly deals with the study of the He-fragmentation of16O nuclei as a result of their interactions with nuclear emulsion at 200A GeV. The data being analyzed consist of 1088 inelastic16O-Em collisions. The mean free path λ (m.f.p.) of16O ions was calculated and found to be 12.81±0.39 cm. A comparison of the percentage ratios for producing He-projectile fragments (p. f.’s) in16O-Em collisions at the present energies with the corresponding values at different energies enables to test the limiting fragmentation hypothesis. The multiplicity distribution of the He-p.f.’s exhibits a KNO scaling. The projected angular distribution of these fragments is typically Gaussian-shaped. The nuclear temperature of the emitting system is inferred from the projected angular distribution of theZ=2 p.f.’s and is approximately equal to the projectile nuclear binding energy, indicating a small energy transfer between target and fragment.

On slow-particle production in 200A GeV16O-emulsion interactions

SummaryThe multiplicity distributions and the correlations of different types of slow particles produced in 200A GeV oxygen-induced interactions with emulsion nuclei are presented. The experimental distributions are studied within the framework of the generalized Andersson-Otterlund-Stenlund (AOS) model for nucleus-nucleus interactions. The generalized (AOS) model fails to describe the present experimental data. Also a systematic comparison using the calculations of VENUS model is made. The grey-particles multiplicity is successfully reproduced by the theoretical multistring model VENUS, while the model is inadequate for explaining the distribution of black particles.

Multiplicities of charged particles in 3.7A GeV32S emulsion interactions

SummaryThe interactions of 3.7A GeV32S ions in nuclear emulsion have been investigated. The multiplicities of charged particles emitted from both projectile and the target nuclei have been studied. The data are compared with current results on the interactions of relativistic ions with emulsion nuclei. The variation of the characteristics of the nucleus-nucleus interactions with the projectile mass number is investigated. The correlations between various kinds of particles of multiple production in32S-Em collisions are presented.

Interaction of relativistic alpha particles in emulsion at 2.1 GeV/c/nucleon

An analysis for 2,000 events produced by 2.1 GeV/c/n alpha particles in nuclear emulsion has been carried out. Multiplicity and angular distributions of charged secondaries have been measured and correlation among them are discussed. The presented data are compared with relevant values from proton and14N interactions with nuclei. The multiplicity distribution of showers has been tested by a modified independent nucleon-nucleus multiple scattering model (INAM) of reference [8], and by the model of reference [12].

Multiplicity distributions of produced particles in 60A GeV16O-emulsion interactions and eclipse effect

SummaryThe shower particles multiplicity distribution produced in 60A GeV16O-Em collisions is studied in the framework of an extended Glauber model in which terms higher than the first (optical limit) in the phase shift expansion are considered. These are the so-called eclipse correction terms. The calculated distribution shows satisfactory agreement with the present experimental data.