Neutrino-induced neutron spallation and the site of the r-process

Abstract

All of the actinides and roughly half the natural abundance of elements with mass number A > 70 come from the rapid neutron capture process, or the r-process. If the r-process, as suggested by many, occurs deep in a supernova, then it is under the influence of an intense neutrino flux. Here we discuss the effects of both charged-current and neutral-current neutrino interactions on the r-process. We show that the multiple-neutron emission induced by both kinds of neutrino interactions can affect the observed r-process abundance pattern significantly. In particular, we find that five nuclei below the r-process abundance peak at A = 195 may be entirely attributed to the neutrino-induced neutron spallation processes following the r-process freeze-out. Furthermore, the deduced neutrino fluence agrees with the conditions in the recent supernova r-process model. These results strongly argue that the r-process occurs in supernovae. They also provide a sensitive probe for the conditions at the supernova r-process site.