Analogous Gamow-Teller and M1 Transitions in T_z = ±½ Mirror Nuclei and in T_z = ±1, 0 Triplet Nuclei relevant to Low-energy Super GT state

¹ Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan
² Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
³ Department of Physics, Tohoku University, Sendai 980-8578, Japan

^* e-mail: fujita@rcnp.osaka-u.ac.jp

Published online: 16 May 2018

Abstract

Nuclei have spin- and isospin-degrees of freedom. Therefore, Gamow-Teller (GT) transitions caused by the στ operator (spin-isospin operator) are unique tools for the studies of nuclear structure as well as nuclear interactions. They can be studied in β decays as well as charge-exchange (CE) reactions. Similarly, M1 γ decays are mainly caused by the στ operator. Combined studies of these transitions caused by Weak, Strong, and Electro-Magnetic interactions provide us a deeper understanding of nuclear spin-isospin-type transitions. We first compare the strengths of analogous GT and M1 transitions in the A = 27, T_z = ±½ mirror nuclei ²⁷Al and ²⁷Si. The comparison is extended to the T_z = ±1, 0 nuclei. The strength of GT transition from the ground state (g.s.) of ⁴²Ca to the 0.611 MeV first J^π = 1⁺ state in ⁴²Sc is compared with that of the analogous M1 transition from the 0.611 MeV state to the T = 1, 0⁺ g.s. (isobaric analog state: IAS) in ⁴²Sc. The 0.611 MeV state has the property of Low-energy Super GT (LeSGT) state, because it carries the main part of the GT strength of all available transitions from the g.s. of ⁴²Ca (and ⁴²Ti) to the J^π = 1⁺ GT states in ⁴²Sc.