Transparencies of complex nuclei to photoproduced pions and recoil nucleons

Abstract

In the high-energy photonuclear research it is very important to study the probability that a pion and/or a recoil nucleon produced by the interaction of a high-energy photon with a complex nucleus, escape from the nucleus without any interaction, i.e. the transparency of the nucleus to the photopions and recoil nucleons. The only publication available in this field is the paper of Roos and PETERSON (1) on the photodissociation of complex nuclei at energies between the mesonic threshold and 1150 MeV. In their work, Roos and PETERSON used the transparency values of METROPOLIS et al. (2.3) for pionand nucleon-initiated cascades, with the simple modification of doubling those transparencies to account for the fact that in the case of photon-initiated cascades, pions and recoil nucleons originate within the nuclei and so have an average path length smaller than that for pions and nucleons impinging from the outside. Roos and PETERSON estimated that the path length in the latter case was two times that for particles originated by photons in the nucleus. The present paper reports the calculation of transparencies for pions and recoil nucleons originated by interaction of high-energy photons with complex nuclei (energy range (0.3-1.0) GeV). The calculation is based on the following assumptions: