Neutrinos in core-collapse supernovae and nucleosynthesis

Neutrino interactions are a key component of the mechanism for supernova explosions. They also play an important role in the associated nucleosynthesis. Nevertheless, a number of issues remain to be resolved. In this review we summarize research by our group and others on some of these issues. Foremost is the role of neutrinos in the explosion itself. Much effort is now invested in understanding the transport of neutrinos from the core and the role of neutrino heated convection in the outer envelopes. In addition to the neutrino transport issues, we review some current topics in neutrino-induced nucleosynthesis (the ν- and νp-processes). We review some current issues regarding the synthesis of the ν-process isotopes ¹⁸⁰Ta and ¹³⁸La and summarize the application of the ν-process chronometers, ^{136, 138}Ce, ¹³⁸La, and ⁹²Nb. We also consider the light ν-process isotopes ⁷Li and ¹¹B and summarize how neutrino oscillations and nucleosynthesis might constrain the neutrino mass hierarchy. We will also review the current dilemma regarding the nucleosynthesis of heavy elements by rapid neutron capture in the neutrino energized wind above the nascent neutron star. We also review the crucial role of neutrino reactions and heating above the high-temperature accretion disc around the black hole of a failed supernova (collapsar model). This collapsar model for long-duration gamma ray bursts is a possible site for r-process nucleosynthesis. We present numerical r-process calculations in the context of a magnetohydrodynamics + neutrino pair heated collapsar simulation. Neutrino heating of the jet is crucial for achieving the required relativistic outflow and at the same time generating material with a high neutron excess. During the late time evolution of the jet an r-process-like abundance distribution is formed within neutrino heated regions of the relativistic outflowing jet. Indeed, sufficient mass is ejected within the flow to account for the observed r-process abundance distribution along with the large dispersion in r-process elements observed in metal-poor halo stars. Finally, we discuss the nuclear physics issues and possible role of relic supernova neutrinos in resolving the supernova rate problem.