Reactor measurement of θ12; Secret of the power

We demonstrate enormous power of dedicated reactor experiment for θ12 with a detector placed at around the first oscillation maximum, which we call “SADO”. It allows determination of sin2θ12 to the accuracy of ≃2% at 1σ CL, which surpasses all the method so far proposed. Unlike reactor θ13 experiments, the requirement for the systematic error is very mild, ≃4%, which makes it an even more feasible experiment. If we place a detector at ∼60 km away from the Kashiwazaki-Kariwa nuclear power plant, 0.5 kt⋅yr exposure of SADO is equivalent to ∼100 kt⋅yr exposure of KamLAND assuming the same systematic error.