The Reactor Antineutrino Anomaly

Early 2011 new reactor antineutrino spectra have been provided for U-235, Pu-239, Pu-241, and U-238, increasing the mean flux by about 3 percent. The authors reevaluated the ratio of observed event rate to predicted rate of 19 published experiments at reactor-detector distances below 100 m, found to be 0.943 +/- 0.023. The deviation from unity, significant at 98.6% C.L., is now being refered as 'the reactor antineutrino anomaly'. The compatibility of our results with the existence of a fourth non-standard neutrino state driving neutrino oscillations at short distances is discussed. The combined analysis of reactor data, gallium solar neutrino calibration experiments data disfavors the no-oscillation hypothesis at 99.8% C. L. The oscillation parameters are such that vertical bar Delta m(new)(2)vertical bar > 1.5 eV(2) (95%) and sin(2)(2 theta(new)) = 0.14 +/- 0.08 (95%).