Nuclear disintegrations produced in nuclear emulsions by α-particles of great energy

Abstract

A study of nuclear disintegrations caused by α-particles of primary cosmic radiation with energies > 5 BeV per nucleon, has been carried out. In a systematic survey in nuclear emulsions using 'along the track' scanning method, 479 α-particles with a total track length of 40·84 metres and 242 interactions were obtained. From the angular distribution of shower particles associated with these interactions, a procedure has been found for distinguishing protons, which originally formed part of the incident α-particle and which have not taken part in the interaction, from other charged particles. The mean free path for nuclear interaction in G-5 emulsion is found to be 17·5±1·1 cm. (68·9±4·3 gm./cm.²). Assigning both to the incident α-particle and to the target nuclei a radius R=r _oA^1/2, one obtains an effective nuclear radius r _o=1·13± 0·04 ×10^-13 cm. Using the number of protons emerging from disintegrations of heavy nuclei (Silver and Bromine) without having participated in the interaction (as can be deduced from the angular distribution) and assuming spherical nuclei of uniform density, the mean free path of nucleons in nuclear matter is calculated to be less than 3·2×10^-13 cm.