The Reactor Anomaly after Daya Bay and RENO

TL;DR

This paper investigates the reactor neutrino anomaly, its implications for sterile neutrinos, and how cosmological models can accommodate or resolve the observed discrepancies in neutrino experiments.

Contribution

It provides a comprehensive analysis combining reactor neutrino data with cosmological constraints, highlighting the potential for sterile neutrinos and chameleon mass models to explain anomalies.

Findings

The anomaly is consistent across short baseline experiments and suggests revising RENO's theta_13 result.

A quintom cosmology can accommodate sterile neutrinos with appropriate masses.

Chameleon mass models satisfy cosmological bounds and reduce experimental tensions.

Abstract

Gallium and short baseline reactor neutrino experiments indicate a short-distance anomalous disappearance of electron antineutrinos which, if interpreted in terms of neutrino oscillations, would lead to a sterile neutrino mass inconsistent with standard cosmological models. This anomaly is difficult to measure at 1 km baseline experiments because its disappearance effects are degenerate with that of theta_13. The flux normalization independent measurement of theta_13 at Daya Bay breaks this degeneracy, allowing an unambiguous differentiation of 1-3 neutrino oscillations and the anomalous disappearance at Double Chooz and RENO. The resulting anomaly is consistent with that found at very short baselines and suggests a downward revision of RENO's result for theta_13. A MCMC global analysis of current cosmological data shows that a quintom cosmology is just compatible at 2 sigma with a sterile neutrino with the right mass to reproduce the reactor anomaly and to a lesser extent the gallium and LSND/MiniBooNE anomalies. However models in which the sterile neutrino acquires a chameleon mass easily satisfy the cosmological bounds and also reduce the tension between LSND and KARMEN.