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, revealing a significant discrepancy with theoretical calculations and suggesting the need for revising the U-235 flux estimates.

Contribution

It provides a more precise experimental determination of the U-235 antineutrino cross section per fission, highlighting potential inaccuracies in current flux calculations.

Findings

U-235 cross section per fission is more precise and differs from theoretical value by 2.2 sigma

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

Indicates likely need to revise U-235 flux calculations

Abstract

We consider the possibility that the reactor antineutrino anomaly is due to a miscalculation of one or more of the $^{235}\text{U}$, $^{238}\text{U}$, $^{239}\text{Pu}$, and $^{241}\text{Pu}$ reactor antineutrino fluxes. 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. We conclude that it is very likely that at least the calculation of the $^{235}\text{U}$ flux must be revised.