Fragmentation of a carbon nucleus into three alpha particles at an incident momentum of 4.2 GeV/c per nucleon in a propane bubble chamber

The coherent dissociation C-12 --> 3 alpha on a carbon target at an incident momentum of 4.2 GeV/c per nucleon is observed, and its cross section is estimated. The dependence of the cross section on the target mass number is investigated. The momentum characteristics and correlations of a particles from coherent dissociation as observed in the laboratory system and in the rest frame of the nucleus undergoing fragmentation are compared with those for incoherent transitions and those for heavier target nuclei. The mechanism of the dissociation C-12 --> 3 alpha is shown to depend strongly on the target mass number and on the character of nucleus-nucleus interaction.