Multiplicities of forward$ndash$backward particles in 32S$ndash$emulsion interactions at 4.5 A GeV/c

Abstract

An exclusive study of the characteristics of the interactions accompanied by the backward emission (θLab ≥ 90°) of relativistic and fast hadrons in the collisions of 4.5 A GeV/c 32S beam with emulsion nuclei is carried out. The experimental multiplicity distributions of different particles emitted in the forward (θLab < 90°) and backward hemispheres due to the interactions with the two emulsion components (CNO, AgBr) are presented and analysed. The correlations between the multiplicities of the different emitted particles are also investigated. This study reveals that there are signatures for a collective mechanism, which plays a role in the production of particles in the backward hemisphere. Hence, the backward multiplicity distribution of the emitted shower or grey particles at 4.5 A GeV/c incident momentum can be represented by a decay exponential law formula independent of the projectile size. The exponent of the power was found to increase with decreasing target size. The experimental data favour the idea that the backward particles were emitted due to the decay of the system in the latter stage of the reaction. While the mean values of the shower particles emitted in the forward hemisphere ⟨nfs⟩ are strongly dependent on the projectile size and incident energy, the mean value of the multiplicity of the shower particles flying into the backward hemisphere ⟨nbs⟩ are found to be only a function of the target size (i.e. impact parameter). Therefore, the results yield quite interesting information regarding the mechanism of the backward particle production in heavy ion interactions. The present data are believed to support the mechanism, which considers the backward particle production as a consequence of the isotropic decay of a highly excited target system, in its rest frame, after the forward particle emission.

Results on the scaling of multiplicity distributions of fast target fragments in high energy nucleus-nucleus collisions

“…Each beam track was carefully followed up to a distance of 5cm or until it interacts with an emulsion nucleus. Other details about irradiations and scanning are given in earlier publications [6][7][8][9]. At all energies, the total samples of inelastic interactions with emulsion nuclei were analyzed by studying the tracks emitted from each interaction detected.…”

Interactions in nuclear emulsion detector irradiated by a-particle

“…Consequently, the produced compound nucleus will de-excite and decay by emitting this excess number of backward hadrons. Such a mechanism of compound target nucleus was discussed in experiments (29,30) . Therefore, regarding the nuclear limiting fragmentation beyond 1A GeV, the projectile energy cannot be considered an effective parameter in the backward production and consequently does not mean that, this system of particle production is a creation system.…”

Multiplicity characteristics in relativistic24Mg-nucleus collisions

“…The dependence of the average values of shower, gray, and black particles on interaction centrality degrees is also studied in this work. This degree could be sufficiently indicated by the value of N h [28][29][30][31] such that as the interaction becomes more central, the value of N h increases. Consequently, the present interactions are classified into five main groups with N h ranging from 0-1, 2-7, 8-15, 16-27 or 28.…”

“…Next, we check the effect of both the interaction centrality degree and the projectile mass number, A Proj , on the forward-backward ratios for shower and gray [24,28,[32][33][34][35]] that the backward shower particle production is a consequence of a decay of the most high excited target system after the emission of the forward particles and hence, such production depends mainly on the target size. The results shown in Table 4 agree with the previous conclusion where the (F/B) s ratios decrease with the increase of N h , i.e.…”