Central collisions of fast particles with heavy nuclei

Abstract

The central collisions of 70 GeV/c protons with Ag, Br and Pb nuclei have been studied, with the help of BR-2 photoemulsion and emulsion of the same constitution loaded with Pb nuclei. It is shown that the average multiplicity of produced particles (s-particles) increases slowly with increasing the atomic weight of the target nucleus. The ratio of the average multiplicity for these particles to the average charged particle multiplicity for protonproton interactions equals 3.2 for p-Ag, Br and 3.5 for p-Pb. The average multiplicities of particles from nuclear disintegration with energies for protons from 26 up to 400 MeV (gparticles) are 14.2_+0.8 for p-Ag, Br and 23.0_+ 1.0 for p-Pb corresponding to the emission of about half of all nucleons from the nucleus at the first rapid stage of interaction. The difference of the s-particle pseudorapidity distributions for p-Ag, Br, Pb and p-p interactions at pseudorapidities larger than 4.2 can be explained by successive interactions of the incident proton with nucleus nucleons.Recently there have been intense experimental and theoretical efforts to study inelastic hadron-nucleus collisions. Experiments with nuclei as targets offer the unique opportunity for studying the space-time development of the particle production process. Also, there has been great interest to investigate the nucleus excitation and disintegration mechanisms, particularly the shock wave model. Central collisions of fast particles with heavy nuclei are suitable for such investigations. In this case the incident particle traverses the nucleus diameter. The central collisions of 70GeV/c protons with Ag l~ Br s~ and Pb 2~ nuclei have been studied in our work. Two types of emulsion were used: standard one BR-2 and another emulsion of the same constitution loaded with Pb nuclei by special technique at the High Energy Laboratory of JINR. Our statistics is 147 events. Nearly one half of these events is p-Ag, Br interactions and the other half p-Pb. Stars, having the number of heavily ionizing tracks N h > 28 in standard emulsion plates, were selected as central collisions with Ag, Br. In [1] it is shown that in these events a complete destruction of the target nucleus takes place and there is no observable residual nucleus with a measurable mass. The average value of the total charge of h-particles per event <Z>=41. The stars, having N h > 40 in loaded emulsion plates, were picked as central collisions with Pb (for these stars <Z> =62). The average multiplicities and the median angles 0 m for the generated particles (s-particles, relativistic particles) and particles from nucleus disintegration with energies for protons from 26 up to 400MeV (gparticles) are summarized in Table 1.

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Further Studies of BURSTS and Spallation in High-Energy Heavy Ion Reactions

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