Joint Determination of Reactor Antineutrino Spectra from $^{235}$U and $^{239}$Pu Fission by Daya Bay and PROSPECT

TL;DR

This study combines data from Daya Bay and PROSPECT to accurately determine the antineutrino spectra from $^{235}$U and $^{239}$Pu fissions, reducing uncertainties and providing a new reference for reactor neutrino research.

Contribution

It presents the first combined analysis of $^{235}$U and $^{239}$Pu spectra from low- and highly enriched uranium reactors, improving spectral shape accuracy.

Findings

Spectra from Daya Bay and PROSPECT are consistent.

Uncertainty in $^{235}$U spectral shape reduced to about 3%.

Provides a data-based reference for future reactor antineutrino experiments.

Abstract

A joint determination of the reactor antineutrino spectra resulting from the fission of $^{235}$U and $^{239}$Pu has been carried out by the Daya Bay and PROSPECT collaborations. This Letter reports the level of consistency of $^{235}$U spectrum measurements from the two experiments and presents new results from a joint analysis of both data sets. The measurements are found to be consistent. The combined analysis reduces the degeneracy between the dominant $^{235}$U and $^{239}$Pu isotopes and improves the uncertainty of the $^{235}$U spectral shape to about 3\%. The ${}^{235}$U and $^{239}$Pu antineutrino energy spectra are unfolded from the jointly deconvolved reactor spectra using the Wiener-SVD unfolding method, providing a data-based reference for other reactor antineutrino experiments and other applications. This is the first measurement of the $^{235}$U and $^{239}$Pu spectra based on the combination of experiments at low- and highly enriched uranium reactors.