Forbidden transitions in nuclear weak processes relevant to neutrino detection, nucleosynthesis and evolution of stars

¹ Department of Physics, College of Humanities and Sciences, Nihon University, Setagaya-ku,Tokyo, 156-8550, Japan
² National Astronomical Observatory of Japan, Mitaka, Tokyo, 181-8588, Japan
³ Reseach Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Meguro, Tokyo, 152-8550, Japan
⁴ Department of Astronomy, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
⁵ Max-Planck-Institut fur Gravitationsphysik (Albert-Einstein-Institute), Am Muhlenberg 1, D-14476, Potsdam-Golm, Germany
⁶ Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, 277-8583, Kashiwa, Chiba, Japan

^* Corresponding author: suzuki@phys.chs.nihon-u.ac.jp

Published online: 4 December 2019

Abstract

The distribution of the spin-dipole strengths in ¹⁶O and neutrino-induced reactions on ¹⁶O areinvestigated by shell-model calculations with new shell-model Hamiltonians. Chargedcurrent and neutral-current reactioncross sections are valuated in various particle and γ emission channels as well as the total ones at neutrinoenergies up to Eν≈ 100 MeV. Effects of multiparticle emission channels, especially the αp emission channels, on nucleosynthesis of ¹¹B and ¹¹C in core-collapse supernova explosions are investigated. The MSW neutrino oscillation effects oncharged-current reaction cross sections are investigated for future supernova burst. Electron capture rates for a forbidden transition ²⁰Ne(O_g.s.⁺) → ²⁰F(2_g.s.⁺) in stellar environments are evaluated by the multipole expansion method with the use of shell model Hamiltonians, and compared with those obtained by a prescription that treats the transition as an allowed GamowTeller (GT) transition. Different electron energy dependence of the transition strengths between the two methods is found to lead to sizable differences in the weak rates of the two methods.