Fission of heavy $Lambda$ hypernuclei with the Skyrme-Hartree-Fock approach

Fission-related phenomena of heavy $Lambda$ hypernuclei are discussed with the constraint Skyrme-Hartree-Fock+BCS (SHF+BCS) method, in which a similar Skyrme-type interaction is employed also for the interaction between a $Lambda$ particle and a nucleon. Assuming that the $Lambda$ particle adiabatically follows the fission motion, we discuss the fission barrier height of $^{239}_{Lambda}$U. We find that the fission barrier height increases slightly when the $Lambda$ particle occupies the lowest level. In this case, the $Lambda$ particle is always attached to the heavier fission fragment. This indicates that one may produce heavy neutron-rich $Lambda$ hypernuclei through fission, whose weak decay is helpful for the nuclear transmutation of long-lived fission products. We also discuss cases where the $Lambda$ particle occupies a higher single-particle level.

Neutrino-Nucleus Reaction Cross Sections for Light Element Synthesis in Supernova Explosions

The neutrino-nucleus reaction cross sections of 4He and 12C are evaluated using new shell model Hamiltonians. Branching ratios of various decay channels are calculated to evaluate the yields of Li, Be, and B produced through the nu-process in supernova explosions. The new cross sections enhance the yields of 7Li and 11B produced during the supernova explosion of a 16.2 M_odot star model compared to the case using the conventional cross sections by about 10%. On the other hand, the yield of 10B decreases by a factor of two. The yields of 6Li, 9Be, and the radioactive nucleus 10Be are found at a level of 10^{-11} M_odot. The temperature of nu_{mu,tau}- and bar{nu}_{mu,tau}-neutrinos inferred from the supernova contribution of 11B in Galactic chemical evolution models is constrained to the 4.3-6.5 MeV range. The increase in the 7Li and 11B yields due to neutrino oscillations is demonstrated with the new cross sections.