Reevaluating reactor antineutrino spectra with new measurements of the ratio between 235U and 239Pu β spectra

We report a reanalysis of the reactor antineutrino energy spectra based on the new relative measurements of the ratio R = S-e(5)/S-e(9) between cumulative beta spectra from U-235 and Pu-239, performed at a research reactor in National Research Centre Kurchatov Institute (KI). A discrepancy with the beta spectra measured at Institut Laue-Langevin (ILL) was observed, indicating a steady excess of the ILL ratio by the factor of 1.054 +/- 0.002. We find a value of the ratio between inverse beta decay cross section per fission for U-235 and Pu-239: ((5)sigma(f )/( 9)sigma(f))(K1) = 1.45 +/- 0.03, and then we reevaluate the converted antineutrino spectra for U-235 and U-238. We conclude that the new predictions are consistent with the results of Daya Bay and STEREO experiments.

Automated summary

A reanalysis of the reactor antineutrino energy spectra based on new measurements revealed discrepancies between different labs, leading to consistent predictions with other experiments.