Ab initio calculations of reactor antineutrino fluxes with exact lepton wave functions

Understand

New \textit{ab initio} calculations of the isotopic reactor antineutrino fluxes are provided with exact numerical calculations of the lepton wave functions, assuming all the decay branches are allowed GT transitions.

• We illustrate that the analytical Fermi function and finite size effect each could have the largest spectral deviation of $\mathcal{O}(10\%)$, whereas the effect of their combination could result in spectral deviations at the level of 5%-10%.
• Meanwhile, we also find that several forms of the extended charge distributions have negligible effects on the spectral variation.
• Using the state-of-the-art nuclear databases, compared to usual \textit{ab initio} calculations using the analytical single beta decay spectrum, our new calculation shows sizable but opposite spectral deviations at the level of 2%-4% for the cumulative antineutrino and electron energy spectra which may partially contribute to the observed spectral excess in the high energy antineutrino range.