Abstract
Stars shine with the energy caused by strong-interaction processes in nuclei. However, a careful observation suggests that they are usually controlled by weak-interaction processes. Gamow-Teller (GT) transitions in nuclei are the most common nuclear weak process in the Universe and they are called “allowed transitions” in β decay. They also play important roles in neutrino-induced reactions, e.g., in Supernovae.
Studying GT transitions can contribute a lot for the understanding of nuclear structure as well as nuclear interactions. Note that nuclei consist of two kinds of fermions, i.e., protons and neutrons having a spin of 1/2. Therefore, GT transitions caused by the simple “spin-isospin (δτ) operator” are good probes to reveal the critical properties of nuclei.
GT excitations are studied by β decays and charge-exchange (CE) reactions. Although β decays can provide the absolute GT transition strengths, they can only access those states situated lower than the decay Q-values. In contrast, (3He, t) CE reactions can study GT excitations up to high excitation energies. Therefore, β decay and CE reactions, caused by the weak and strong interactions, respectively, are complementary tools for the study of GT responses of nuclei.
Coffee and tea will be served 20 minutes prior to the seminar.
Anyone interested is welcome to attend.