Role of ~8Be → 2 α intermediate nuclei in the fragmentation of ~(16)O relativistic nuclei in nuclear track emulsions

摘要

In searches along a track in the chamber irradiated at the Laboratory of High Energies at the Joint Institute for Nuclear Research (JINR, Dubna) with oxygen ions accelerated to a momentum of 4.5 GeV/c per nucleon, 215 events containing two or more doubly charged fragments of the primary nucleus were found. Emission angles in the track-emulsion plane were measured in these events. Their distribution is consistent with that which alpha particles are expected to have in an oxygen nucleus prior to its interaction with a track-emulsion nucleus. Events of the ~(16)O → 2 ~8Be → 4α type were discovered for the first time. They are treated as events of the coherent electromagnetic dissociation of an oxygen nucleus. Among all events, about 14% of the ~8Be → 2α decays proceed through the ground state of spin-parity 0 ~+; an approximately the same fraction of such decays proceed through the first excited state of spin-parity 2 ~+.