Reactor neutrino oscillation studies with KamLAND

KamLAND, the 1000 t liquid scintillator detector utilizing nuclear power reactors distributing effectively ∼180 km from the experimental site, has performed a search for reactor neutrino oscillations. Results obtained from the baseline show evidence for reactor neutrino disappearance, while previous searches at less than 1 km showed consistent flux, as expected. This provides a resolution for the long-standing solar neutrino problem if combined with results from solar neutrino experiments. KamLAND with increased statistics also provided evidence of spectral distortion as expected from the neutrino oscillation and, if converted to the L/E distribution, it shows clear oscillatory behaviour of neutrino propagation. Consequently, the results have a good sensitivity on neutrino oscillation parameters and a precise determination of Δm² has been realized.