Another neutrino detector sees neutrino flavor deficit

Ars Technica : China’s Daya Bay neutrino detector analyzes a beam of electron antineutrinos produced by nearby nuclear reactors. The detector counts how many of the particles have experienced flavor oscillation and become either muon or tau antineutrinos. After nearly eight months of operation, the facility has detected more than 300 000 neutrinos. However, the number of flavor oscillations has not matched what scientists predicted, and this is not the first detector to note the discrepancy. But none of the experiments have had a strong enough—5 sigma—signal to conclude outright that the discrepancy is real. One theory suggests that there are flavor-neutral, or “sterile,” neutrinos. Perhaps on a related note, Daya Bay also saw an unexpectedly large, though also not quite 5 sigma, signal in the energy level of the neutrinos. If that signal proves to be real, it could mean that nuclear reactors aren’t producing as many neutrinos as expected.