Innovative ²³⁸U fission yield evaluation to address the reactor antineutrino puzzle

The antineutrino spectrum from ²³⁸U has been singled out by A. Hayes et al. as a likely source of the excess of antineutrinos at 5 MeV with respect to the Huber-Mueller model, colloquially known as ‘the bump’, observed by Daya Bay, Double Chooz and RENO. The current ²³⁸U antineutrino reference spectrum was obtained using nuclear databases by Mueller et al., as the quality of the corresponding electron spectra does not allow for a meaningful conversion. In this work, we calculated independent and cumulative ²³⁸U fission yields (FY) incorporating new data and modelling tools. Our starting point was the high-resolution mass yields measured at GELINA, obtaining isotopic FY with the assistance of the GEF code and in consultation with yields from the SOFIA experiment. The latest measurements of isomeric ratios were used to obtain independent yields. Finally, cumulative FY were obtained with the latest nuclear structure data. Comparison of the newly calculated FY with recent data as well as a preliminary ²³⁸U antineutrino spectrum will be presented.