Araki, T (reprint author), Tohoku Univ, Res Ctr Neutrino Sci, Sendai, Miyagi 9808578, Japan.
The Kamioka Liquid scintillator Anti-Neutrino Detector is used in a search for single neutron or two-neutron intranuclear disappearance that would produce holes in the s-shell energy level of C-12 nuclei. Such holes could be created as a result of nucleon decay into invisible modes (inv), e.g., n -> 3 nu or nn -> 2 nu. The deexcitation of the corresponding daughter nucleus results in a sequence of space and time-correlated events observable in the liquid scintillator detector. We report on new limits for one- and two-neutron disappearance: tau(n -> inv)> 5.8x10(29) years and tau(nn -> inv)> 1.4x10(30) years at 90% C.L. These results represent an improvement of factors of similar to 3 and > 10(4) over previous experiments.