Indexed on: 08 Mar '13Published on: 08 Mar '13Published in: Frontiers of Physics
Neutrinos are elementary particles in the Standard Model. Neutrino oscillation is a quantum mechanical phenomenon beyond the Standard Model. Neutrino oscillation can be described by two independent mass-squared differences Δm212, Δm312 (or Δm322) and a 3 × 3 unitary matrix, containing three mixing angles θ12, θ23, θ13, and one charge-parity (CP) phase. θ12 is about 34° and determined by solar neutrino experiments and the reactor neutrino experiment KamLAND. θ23 is about 45° and determined by atmospheric neutrino experiments and accelerator neutrino experiments. θ13 can be measured by either accelerator or reactor neutrino experiments. On Mar. 8, 2012, the Daya Bay Reactor Neutrino Experiment reported the first observation of non-zero θ13 with 5.2 standard deviations. In June, with 2.5× previous data, Daya Bay improved the measurement of sin22θ13 = 0.089 ± 0.010(stat) ± 0.005(syst).