Search for n - (n)over-bar oscillation in Super-Kamiokande

A search for neutron-antineutron (n - (n) over bar n) oscillation was undertaken in Super-Kamiokande using the 1489 live-day or 2.45 x 10(34) neutron-year exposure data. This process violates both baryon and baryon minus lepton numbers by an absolute value of two units and is predicted by a large class of hypothetical models where the seesaw mechanism is incorporated to explain the observed tiny neutrino masses and the matter-antimatter asymmetry in the Universe. No evidence for n - (n) over bar oscillation was found; the lower limit of the lifetime for neutrons bound in O-16, in an analysis that included all of the significant sources of experimental uncertainties, was determined to be 1.9 x 10(32) years at the 90% confidence level. The corresponding lower limit for the oscillation time of free neutrons was calculated to be 2.7 x 10(8) s using a theoretical value of the nuclear suppression factor of 0.517 x 10(23) s(-1) and its uncertainty.