Coherent fragmentation of {sup 12}C nuclei of momentum 4.5 GeV/c per nucleon through the {sup 8}Be{sub g.s.}+{sup 4}He channel in a nuclear photoemulsion containing lead nuclei

• Published in: Physics of atomic nuclei Vol. 80; no. 4
• Main Authors: Belaga, V. V., Gerasimov, S. G., Dronov, V. A., Peresadko, N. G., Pisetskaya, A. V., Rusakova, V. V., Fetisov, V. N., Kharlamov, S. P., Shesterkina, L. N.
• Format: Journal Article
• Language: English
• Published: United States 15.07.2017
• Subjects: ALPHA PARTICLES; BERYLLIUM 8; CARBON 12; COULOMB EXCITATION; CROSS SECTIONS; GEV RANGE 01-10; GROUND STATES; HELIUM 4; JINR NUCLOTRON; LEAD; MEV RANGE; MOMENTUM TRANSFER; NUCLEONS; PARTICLE TRACKS; PHOTOGRAPHIC EMULSIONS; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; TRANSVERSE ENERGY; TRANSVERSE MOMENTUM
• ISSN: 1063-7788; 1562-692X
• DOI: 10.1134/S1063778817040044

A two-particle channel in which an unbound nucleus of {sup 8}Be in the ground state ({sup 8}Be{sub g.s.}) was one of the fragments was selected among events where {sup 12}C nuclei of momentum 4.5 GeV/c per nucleon undergo coherent dissociation into three alpha particles. The events in question were detected in a track nuclear photoemulsion containing lead nuclei, which was irradiated at the synchrophasotron of the Laboratory of High Energies at the Joint Institute for Nuclear Research (JINR, Dubna). The average transverse momentum of alpha particles produced upon the decay of {sup 8}Be{sub g.s.} nuclei was 87±6 MeV/c, while that for “single” alpha (α{sub s}) particles was 123±15 MeV/c. The average value of the transverse-momentum transfer in the reaction being considered, Pt(12C), was 223 ± 20 MeV/c. The average value of the cross section for this channel involving Ag and Br target nuclei was 13 ± 4 mb, while the cross section for the reaction on the Pb nucleus was 40 ± 15 mb. The Coulomb dissociation contribution evaluated on the basis of the number of events where the momentum P{sub t}({sup 12}C) did not exceed 0.1 GeV/c saturated about 20%. In nine events, the measured total transverse energy of the fragments in the reference frame comoving with the decaying carbon nucleus did not exceed 0.45 MeV, which did not contradict the excitation of the participant {sup 12}C nucleus to the level at 7.65 MeV. The average value of the transverse momentum in those events was 234 ± 25 MeV/c.