Neutrino-nuclear response and photonuclear reactions

Photonuclear reactions are shown to be used for studying neutrino (weak) nuclear responses involved in astroneutrino nuclear interactions and double beta decays. Charged current weak responses for ground and excited states are studied by using photonuclear reactions through isobaric analog states of those states, while neutral current weak responses for excited states are studied by using photonuclear reactions through the excited states. The weak interaction strengths are studied by measuring the cross sections of the photonuclear reactions, and the spin and parity of the states are studied by measuring angular correlations of particles emitted from the photonuclear reactions. Medium-energy polarized photons obtained from laser photons scattered off GeV electrons are very useful. Nuclear responses studied by photonuclear reactions are used to evaluate neutrino (weak) nuclear responses, i.e., nuclear beta and double beta matrix elements and neutrino-nuclear interactions, and to verify theoretical calculations for them.