Centrality dependence of total disintegration of target nuclei in high energy nucleus–nucleus interactions

A study of centrality dependence of target fragmentation and multiparticle production has been carried out in 16O–AgBr, 22Ne–AgBr, and 28Si–AgBr interactions at 4.1–4.5 AGeV/c for the total disintegrated (TD) events. Average multiplicity of black particles increases linearly with decreasing centrality while average multiplicity of grey and shower particles decreases with decreasing centrality for the TD events. The decrease of average multiplicity of grey particles is linear; on the other hand, in the case of shower particles, the increase is nonlinear. With the increase of the mass of the projectile beam, the average multiplicity of black particles decreases and the average multiplicity of grey particles increases for the TD events. This observation has been explained on the basis of the fireball model; however, in the case of shower particles, average multiplicity increases with increase of projectile mass.

Characteristics of the total disintegration events of emulsion heavy target nuclei caused by O16 and 28Si nuclei at high energies

The present paper deals with the interactions of 16O and 28Si nuclei with emulsion heavy target nuclei (silver (Ag) and bromine (Br)) at 4.5A GeV/c. The results have been analyzed to identify interesting characteristics of the total disintegration (TD) events produced in these interactions. Events having a number of heavily ionizing particles Nh ≥ 28 have been selected in this study. The integral multiplicity distributions for the disintegrated particles from the target nuclei have been used to separate the inelastic interactions with the free hydrogen (H), the light (CNO), and the heavy (AgBr) nuclei. The average multiplicities of the different secondary particles emitted in these interactions have been compared with the corresponding ones of different projectiles nearly at the same momentum. The average multiplicity of the grey particles is found to increase with the mass of the projectile, while the average multiplicity of the black particles is found to decrease with increasing mass of the projectile; this result agrees with the prediction of the fireball model. Also, the dependence of the shower, grey, and black particles produced in the TD events on the mass of the projectile has been studied. Moreover, the dependence of the probability of the TD for the projectile mass as well as the target fragments has also been discussed. The results show that the multiplicity distributions of the shower, grey, and black particles present a Gaussian distribution. Finally, the linear dependence of the grey and compound multiplicities on the black, heavy, and shower particles has also been observed.

The Radio Afterglows of Gamma-Ray Bursts

SummaryRadio afterglow observations continue to provide complementary and sometimes unique diagnostics on gamma-ray burst explosions, their progenitors and their environments. In this review we will first describe current search strategies and the observational properties of the detected sample. In the second part of this review we will follow the evolution of a typical radio afterglow, describe the diverse phenomenology that is observed, and interpret these observations within the framework of the fireball model.