Speaker
Description
Important roles of Gamow-Teller transitions have been studied for electron-capture and $\beta$-decay processes at stellar environments [1, 2] as well as $\nu$-nucleus reactions [3]. Importance of first-forbidden transitions in $\beta$-decay rates of N=126 isotones have been shown, and the short half-lives obtained were used to study r-process nucleosynthesis in core-collapse supernova explosions (SNe) and binary neutron-star mergers [4].
Here, we focus more on the roles of forbidden transitions in nuclear weak processes. $\nu$-induced reactions on $^{16}$O, where spin-dipole transitions are dominant, are studied with new shell-model Hamiltonians [5] and SN$\nu$ detection and $\nu$ mass hierarchy dependence of the cross sections [6] as well as nucleosynthesis of light elements such as $^{11}$B and $^{11}$C in SNe [5] are discussed.
Next, we study e-capture processes on $^{20}$Ne which become important in late stage of the evolution of O-Ne-Mg cores in stars. The transition to the ground state in $^{20}$F (2$^{+}$) is a second-forbidden transition and is important in certain ranges of densities and temperatures [7]. Electron-capture rates for the transition are evaluated with the multipole expansion method, and compared with a simple evaluation using a constant parametrized strength obtained from the beta-decay experiment [8]. Energy dependence of the second-forbidden transition strength is found to lead to a significant difference in the capture rates from the simple parametrized method.
[1] T. Suzuki, H. Toki, and K. Nomoto, ApJ. 817, 163 (2016)
[2] K. Mori et al., ApJ. 833, 179 (2016) (2009)
[3] T. Suzuki et al., Phys. Rev. C 74, 0407 (2006)
[4] T. Suzuki et al, ApJ. 859, 1 (2018)
[5] T. Suzuki, S. Chiba, T. Yoshida, K. Takahashi, and H. Umeda, Phys. Rev. C 98, 034613 (2018)
[6] K. Nakazato, T. Suzuki, and M. Sakuda, PTEP 2018, 123E02 82018)
[7] G. Martinez-Pinedo et al., Phys. Rev. C 89, 045806 (2014)
[8] O. S. Kirseborn et al., arXiv:1805.19149 (2018)
