Experimental study of neutrino oscillations at a fission reactor

Abstract The electron-antineutrino spectrum has been measured at a position 8.75 m from the “point-like” core of the ILL 235 U fission reactor, using the reaction ν e + p → e + + n. Positrons and neutrons were detected in coincidence by means of a low-background liquid scintillator and a 3 He detector system. The observed neutron correlated positron spectrum is consistent with theoretical predictions assuming no neutrino oscillations. Upper limits for the oscillation parameter are presented.