Speaker
Description
With the low angular-momentum transfer in the inelastic scattering of real photons, the photo-excited states often have relevance also for other nuclear processes, in particular weak processes. For example, scattering of neutrinos off atomic nuclei, governed by the weak force, can predominantly excite magnetic-dipole excitations, which subsequently decay via gamma or particle emission, depending on their energy relative to particle thresholds. As such, large-scale neutrino experiments can be sensitive to the detection of, e.g., super-nova neutrinos through the nuclear excitation of the detection material via incoherent neutrino scattering. Furthermore, the spin-M1 operator, which is dominant in the electro-magnetic M1 operator, has a structure analog to the Gamov-Teller operator, which mediates spin-isospin changing electron-capture decays. This analogy between weak and electro-magnetic operators can be exploited to constrain weak processes through the measurement of electro-magnetic properties, in turn interesting for violent astrophysical processes and nucleo-genesis. Another aspect is the sensitivity of nuclear model predictions of weak processes to the structure of the involved nuclear eigenstates, which, in turn, is governed mostly by the strong interaction. The sensitivity of, in particular, isovector nuclear excitations like the scissors mode to the structure of states relevant for double-beta and neutrino-less double-beta decays has previously been tested on key isotopes. These aspects connecting photo-nuclear science and weak-interaction physics will be discussed in view of recent advancements and related present and future experiments using gamma beams.
