We study the role of light neutron-rich nuclei during r-process nucleosynthesis in supernovae. Most previous studies of the r-process have concentrated on the reaction flow of heavy unstable nuclei. Although the nuclear reaction network includes a few thousand heavy nuclei, only limited reaction flow through light-mass nuclei near the stability line has been used in those studies. However, in a viable scenario of the r-process in neutrino-driven winds, the initial condition is a high-entropy hot plasma consisting of neutrons, protons, and electron-positron pairs experiencing an intense flux of neutrinos. In such environments light-mass nuclei as well as heavy nuclei are expected to play important roles in the production of seed nuclei and r-process elements. Thus, we have extended our fully implicit nuclear reaction network so that it includes all nuclei up to the neutron drip line for Z ≤ 10, in addition to a larger network for Z ≥ 10. In the present nucleosynthesis study, we utilize a wind model of massive SNeII explosions to study the effects of this extended network. We find that a new nuclear-reaction flow path opens in the very light neutron-rich region. This new nuclear reaction flow can change the final heavy-element abundances by as much as an order of magnitude.

We study the nucleosynthesis of the light elements 7 Li and 11 B and the rprocess elements in Type II supernovae from the point of view of supernova neutrinos and Galactic chemical evolution. We investigate the influence of the luminosity and average energy (temperature) of supernova neutrinos on these two nucleosynthesis processes. Common models of the neutrino luminosity, which is parameterized by the total energy E ν and decay time τ ν and neutrino temperature are adopted to understand both processes. We adopt the model of the supernova explosion of a 16.2 M ⊙ star, which corresponds to SN 1987A, and calculate the nucleosynthesis of the light elements by postprocessing. We find that the ejected masses of 7 Li and 11 B are roughly proportional to the total neutrino energy and are weakly dependent on the decay time of the neutrino luminosity. As for the r-process nucleosynthesis, we adopt the same models of the neutrino luminosity in the neutrino-driven wind models of a 1.4 M ⊙ neutron star. We find that the r-process nucleosynthesis is affected through the peak neutrino luminosity, which depends on E ν /τ ν . The observed r-process abundance pattern is better reproduced at a low peak neutrino luminosity. We also discuss the unresolved problem of the overproduction of 11 B in the Galactic chemical evolution of the light elements. We first identify that the ejected mass of 11 B is a factor of 2.5-5.5 overproduced in Type II supernovae when one adopts neutrino parameters similar to those in previous studies, i.e., E ν = 3.0 × 10 53 ergs, τ ν = 3 s, and a neutrino temperature T νµ,τ = Tν µ,τ = 8.0 MeV/k. We have to assume E ν ≤ 1.2 × 10 53 ergs to avoid the overproduction of 11 B, which is too small to accept in comparison to the 3.0 × 10 53 ergs deduced from the observation of SN1987A. We here propose to reduce the temperatures of ν µ,τ andν µ,τ to 6.0 MeV/k in a model with E ν ∼ 3.0 × 10 53 ergs and τ ν ∼ 9 s. This modification of the neutrino temperature is shown to resolve the overproduction problem of 11 B while still keeping a successful r-process abundance pattern.