Reactor antineutrino anomaly

Recently, new reactor antineutrino spectra have been provided for ²³⁵U, ²³⁹Pu, ²⁴¹Pu, and ²³⁸U, increasing the mean flux by about 3%. To a good approximation, this reevaluation applies to all reactor neutrino experiments. The synthesis of published experiments at reactor-detector distances <100 m leads to a ratio of observed event rate to predicted rate of 0.976±0.024. With our new flux evaluation, this ratio shifts to 0.943±0.023, leading to a deviation from unity at 98.6% C.L. which we call the reactor antineutrino anomaly. The compatibility of our results with the existence of a fourth nonstandard neutrino state driving neutrino oscillations at short distances is discussed. The combined analysis of reactor data, gallium solar neutrino calibration experiments, and MiniBooNE-ν data disfavors the no-oscillation hypothesis at 99.8% C.L. The oscillation parameters are such that |Δmnew²|>1.5 eV² (95%) and sin²(2θnew)=0.14±0.08 (95%). Constraints on the θ₁₃ neutrino mixing angle are revised.