Precise Determination of the U-235 Reactor Antineutrino Cross Section per Fission

TL;DR

This paper precisely measures the U-235 reactor antineutrino cross section per fission, suggesting the need to revise its flux calculations and providing a more accurate value than previous estimates.

Contribution

It offers a new, more precise measurement of the U-235 antineutrino cross section per fission, highlighting potential inaccuracies in existing flux calculations.

Findings

The U-235 flux calculation likely needs revision.

The measured cross section per fission is more precise than previous theoretical values.

Other fluxes have large uncertainties and are not well constrained by the data.

Abstract

We investigate which among the reactor antineutrino fluxes from the decays of the fission products of $^{235}\text{U}$, $^{238}\text{U}$, $^{239}\text{Pu}$, and $^{241}\text{Pu}$ may be responsible for the reactor antineutrino anomaly if the anomaly is due to a miscalculation of the antineutrino fluxes. We find that it is very likely that at least the calculation of the $^{235}\text{U}$ flux must be revised. From the fit of the data we obtain the precise determination $\sigma_{f,235} = ( 6.33 \pm 0.08 ) \times 10^{-43} \, \text{cm}^2 / \text{fission}$ of the $^{235}\text{U}$ cross section per fission, which is more precise than the calculated value and differs from it by $2.2\sigma$. The cross sections per fission of the other fluxes have large uncertainties and in practice their values are undetermined by the fit.