Some special features of the fragmentation of a relativistic nucleus B-11 in photoemulsion

摘要

Events where two doubly charged fragments are directly formed from a fragmenting nucleus B-11 of momentum 2.75 GeV/c per nucleon are separated, the cascade production of such fragments via the fragmentation channel Be-8 -> 2 alpha being avoided. Where possible, the mass numbers of these doubly charged fragments are determined by using a signal from Coulomb scattering in photoemulsion. It is found that the measured fraction of the isotope He-6 is (9.6 +/- 1.5)%, while its calculated probability is about 12%. The transverse-momenturn distributions obtained experimentally for the isotopes He-3 and He-4 are compatible with a Rayleigh distribution characterized by constant values of 110.4 +/- 6.0 and 127.5 +/- 6.0 MeV/c, respectively. These features of the distributions agree with a purely statistical mechanism of the fragmentation of B-11 nuclei.