Analysis of the Daya Bay Reactor Antineutrino Flux Changes with Fuel Burnup

TL;DR

This paper analyzes Daya Bay reactor antineutrino flux changes with fuel burnup, identifying discrepancies with models and exploring nuclear database-based explanations, but finds insufficient evidence to confirm sterile neutrino existence.

Contribution

It provides a detailed analysis linking flux discrepancies to initial spectral ratios and nuclear data, challenging previous interpretations of anomalies.

Findings

Discrepancies linked to initial $^{235}$U/$^{239}$Pu ratios.

Summation method explains spectral features but predicts an anomaly.

Current data insufficient to confirm sterile neutrinos.

Abstract

We investigate the recent Daya Bay results on the changes in the antineutrino flux and spectrum with the burnup of the reactor fuel. We find that the discrepancy between current model predictions and the Daya Bay results can be traced to the original measured $^{235}$U/$^{239}$Pu ratio of the fission beta spectra that were used as a base for the expected antineutrino fluxes. An analysis of the antineutrino spectra that is based on a summation over all fission fragment beta-decays, using nuclear database input, explains all of the features seen in the Daya Bay evolution data. However, this summation method still predicts an anomaly. Thus, we conclude that there is currently not enough information to use the antineutrino flux changes to rule out the possible existence of sterile neutrinos.