Neutrino–nucleus reactions and their role for supernova dynamics and nucleosynthesis

The description of nuclear reactions induced by supernova neutrinos has witnessed significant progress during the recent years. On one hand this progress is due to experimental data which serve as important constraints to model calculations, on the other hand it is related to advances in nuclear modeling itself and in computer hardware. At the energies and momentum transfers relevant for supernova neutrinos, neutrino–nucleus cross sections are dominated by allowed transitions, however, often with non-negligible contributions from (first) forbidden transitions. For several nuclei, allowed Gamow–Teller strength distributions have been derived from charge-exchange reactions and from inelastic electron scattering data. Importantly the diagonalization shell model has been proven to accurately reproduce these data and hence became the appropriate tool to calculate the allowed contributions to neutrino–nucleus cross sections for supernova neutrinos. Higher multipole contributions are usually calculated within the framework of the Quasiparticle Random Phase Approximation, which describes the total strength and the position of the giant resonances quite well. Both are the relevant quantities for a reliable calculation of the forbidden contributions to the cross sections.The current manuscript reviews the recent progress achieved in calculating supernova-relevant neutrino–nucleus cross sections and discusses its verification by data. Moreover, the review summarizes also the impact which neutrino–nucleus reactions have on the dynamics of supernovae and on the associated nucleosynthesis. With relevance to the supernova dynamics, these include the absorption of neutrinos by nuclei (the inverse of nuclear electron capture which is the dominating weak-interaction process during collapse), inelastic neutrino–nucleus scattering and nuclear de-excitation by neutrino-pair emission. For supernova nucleosynthesis we discuss the role of neutrino-induced reactions for the recently discovered νpνp process, for the rr-process and for the neutrino process, for which neutrino–nucleus reactions have the largest impact. Finally we briefly review neutrino–nucleus reactions important for the observation of supernova neutrinos by earthbound detectors.