Search forn−n¯Oscillation in Oxygen

This Letter reports the results of a search for neutron-antineutron transitions in oxygen, using a water Cherenkov detector of fiducial mass 3300 metric tons located 1570 m (water equivalent) underground. Two independent methods yield 90% -confidence lower limits of 1.7 × ${10}^{31}$ and 2.4 × ${10}^{31}$ yr, respectively, for the partial lifetime of this process. According to recent calculations the latter result corresponds to a lower limit in the range 2.7 × ${10}^7$ to 1.1 × ${10}^8$ sec for the free-neutron oscillation time.