Reactor ? ¯e disappearance in the Double Chooz experiment

The Double Chooz experiment has observed 8249 candidate electron antineutrino events in 227.93 live days with 33.71GW-ton-years (reactor power×detector mass×live time) exposure using a 10.3m3 fiducial volume detector located at 1050m from the reactor cores of the Chooz nuclear power plant in France. The expectation in case of ? 13=0 is 8937 events. The deficit is interpreted as evidence of electron antineutrino disappearance. From a rate plus spectral shape analysis we find sin22? 13=0.109±0.030(stat)±0.025(syst) . The data exclude the no-oscillation hypothesis at 99.8%CL (2.9s).