Reactor Fuel Fraction Information on the Antineutrino Anomaly

TL;DR

This paper investigates the reactor antineutrino anomaly by analyzing Daya Bay data and other experiments, considering active-sterile neutrino oscillations and flux uncertainties, finding a slight preference for oscillations combined with flux variations.

Contribution

It provides a comprehensive analysis combining reactor flux uncertainties and active-sterile neutrino oscillations, highlighting the best-fit models for the anomaly.

Findings

Oscillations disfavored at 2.6-2.5 sigma compared to flux suppression.

Active-sterile oscillations favored at 3.1 sigma over flux suppression.

Composite models with flux variations and oscillations fit data well.

Abstract

We analyzed the evolution data of the Daya Bay reactor neutrino experiment in terms of short-baseline active-sterile neutrino oscillations taking into account the theoretical uncertainties of the reactor antineutrino fluxes. We found that oscillations are disfavored at $2.6\sigma$ with respect to a suppression of the $^{235}\text{U}$ reactor antineutrino flux and at $2.5\sigma$ with respect to variations of the $^{235}\text{U}$ and $^{239}\text{Pu}$ fluxes. On the other hand, the analysis of the rates of the short-baseline reactor neutrino experiments favor active-sterile neutrino oscillations and disfavor the suppression of the $^{235}\text{U}$ flux at $3.1\sigma$ and variations of the $^{235}\text{U}$ and $^{239}\text{Pu}$ fluxes at $2.8\sigma$. We also found that both the Daya Bay evolution data and the global rate data are well-fitted with composite hypotheses including variations of the $^{235}\text{U}$ or $^{239}\text{Pu}$ fluxes in addition to active-sterile neutrino oscillations. A combined analysis of the Daya Bay evolution data and the global rate data shows a slight preference for oscillations with respect to variations of the $^{235}\text{U}$ and $^{239}\text{Pu}$ fluxes. However, the best fits of the combined data are given by the composite models, with a preference for the model with an enhancement of the $^{239}\text{Pu}$ flux and relatively large oscillations.