Event

The Reactor Experiment for Neutrino Oscillation(RENO) started data-taking from August, 2011 and has observed the disappearance of reactor electron antineutrinos to measure the smallest neutrino mixing angle theta13. The experiment has analyzed roughly 2200 days of data to make an accurate measurement of the oscillation amplitude and frequency based on energy and baseline dependent disappearance of reactor antineutrinos. RENO’s precisely measured flux and spectral shape of reactor antineutrinos has shown a deficit in the flux and an excess in the region of 5 MeV relative to the most commonly used model. Furthermore, it has observed fuel-composition dependent variation of reactor antineutrino yield and spectrum. We find that reevaluation of 235U’s antineutrino yield per fission may mostly solve the reactor antineutrino anomaly. We also report a hint of correlation between the 5-MeV excess and the 235U fuel isotope fraction.