Sterile Neutrinos or Flux Uncertainties? - Status of the Reactor Anti-Neutrino Anomaly

Abstract

The $\sim 3\sigma$ discrepancy between the predicted and observed reactor anti-neutrino flux, known as the reactor anti-neutrino anomaly, continues to intrigue. The recent discovery of an unexpected bump in the reactor anti-neutrino spectrum, as well as indications that the flux deficit is different for different fission isotopes seems to disfavour the explanation of the anomaly in terms of sterile neutrino oscillations. We critically review this conclusion in view of all available data on electron (anti)neutrino disappearance. We find that the sterile neutrino hypothesis cannot be rejected based on global data and is only mildly disfavored compared to an individual rescaling of neutrino fluxes from different fission isotopes. The main reason for this is the presence of spectral features in recent data from the NEOS and DANSS experiments. If state-of-the-art predictions for reactor fluxes are taken at face value, sterile neutrino oscillations allow a consistent description of global data with a significance close to $3\sigma$ relative to the no-oscillation case. Even if reactor fluxes and spectra are left free in the fit, a $2\sigma$ hint in favour of sterile neutrinos remains, with allowed parameter regions consistent with an explanation of the anomaly in terms of oscillations.

25 pages, 5 figures. 1 page and table 4 added. Published in JHEP

References in corpus (7)

• Measurement of the solar neutrino capture rate with gallium metal. III: Results for the 2002--2007 data-taking period
• Sterile neutrino search at NEOS Experiment
• First Constraints on the Complete Neutrino Mixing Matrix with a Sterile Neutrino
• The 5 MeV bump - a nuclear whodunit mystery
• Reactor Fuel Fraction Information on the Antineutrino Anomaly
• Precise Determination of the U-235 Reactor Antineutrino Cross Section per Fission
• Reactor antineutrino shoulder explained by energy scale nonlinearities?

Cited by in corpus (6)

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• Flavor-dependent radiative corrections in coherent elastic neutrino-nucleus scattering
• Diagnosing the Reactor Antineutrino Anomaly with Global Antineutrino Flux Data
• A testable hidden-sector model for Dark Matter and neutrino masses
• Mapping reactor neutrino spectra from TAO to JUNO
• BEST potential in testing the eV-scale sterile neutrino explanation of reactor antineutrino anomalies