Single and Double Charge Exchange Excitations of Spin-Isospin Mode

We study the sum rules of double Gamow-Teller (DGT) excitations through double spin-isospin operator (σt­)2 In general, 2+states in the granddaughter nuclei have dominant transition strength in DGT excitations and 0+states are weak, except in T = 1 mother nuclei in which 0+strength is competitive with 2+strength. A possibility to extract the unit cross section for the DGT transition strength is pointed out in the (#x03C3;t­)2 excitation of double isobaric analog state (DIAS) in T = 1 nuclei.

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

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, Tz = ±½ mirror nuclei 27Al and 27Si. The comparison is extended to the Tz = ±1, 0 nuclei. The strength of GT transition from the ground state (g.s.) of 42Ca to the 0.611 MeV first Jπ = 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 Jπ = 1+ GT states in 42Sc.

The nuclear symmetry energy and the breaking of the isospin symmetry: how do they reconcile with each other?

Our current knowledge of the Equation of State of asymmetric nuclear matter around saturation density and of the energy of the Isobaric Analog State in a heavy nucleus such as 208Pb seem to be in contradiction. In Ref. [1], the problem has been highlighted and a solution has been proposed. In the present contribution, we overview the aforementioned work by giving some new details not previously published.