Very Low-Energy Neutrino Interactions

Neutrino-nucleus reaction cross sections are now evaluated rather accurately by shell-model (SM) or SM+RPA calculations based on recent advances in nuclear structure studies. Due to these achievements, reliable constraints on supernova neutrino temperatures as well as neutrino oscillation parameters become possible. Supernova neutrino tempeatures are constrained from abundances of elements obtained by using new nu-nucleus reaction cross sections. A possibility of constructing supernova neutrino spectrum from beta-beam measurements is pointed out. Neutrino mass hierarchy and mixing angle theta(13) can be determined from abundance ratio of Li-7/B-11, which is sensitive to the MSW matter oscillation effects in supernova explosions. Inverted mass hierarchy is shown to be statistically more favored based on a recent analysis of presolar grains. Effects of neutrino-neutrino interactions are also shown to play important roles in r-process nucleosynthesis. Importance and possibilities of direct measurements of nu-induced cross sections on Ar-40 and Pb-208 are discussed for future supernova neutrino detections. Recent calculations of the cross sections for nu-Ar-40 are presented. The need for new theoretical evaluations of the cross sections for nu-Pb-208 is pointed out. Challenges to experiments on coherent elastic scattering are presented.