Speaker: Anna Hayes-Sterbenz, Los Alamos National Laboratory
Abstract: Recent analyses of the anti-neutrino flux from reactors has suggested that shot baseline reactor neutrino experiments saw only about 92.7% of the expected flux, a result is commonly referred to as the Reactor Neutrino Anomaly. In this talk I will present an independent analysis of this anomaly and the underlying nuclear physics determining the shape and magnitude of reactor neutrino spectra. In this analysis, we find that corrections due to forbidden beta-decays of fission fragments result in significant changes to the shape of the spectrum. These changes, which have not been taken into account in earlier anomaly analyses, leads to more anti-neutrinos being emitted at low (<2.5 MeV) and high energies (>4.5 MeV), and fewer anti-neutrinos between 2.5-4.5 MeV. The uncertainty in the shape of the spectrum also increases when the forbidden transitions are included. The measured spectrum from the near detector at Daya Bay should greatly help to reduce these uncertainties.