  We have measured de-excitation gamma-rays from the s-hole state in 15N
produced via the 16O(p,2p)15N reaction in relation to the study of the nucleon
decay and the neutrino neutral-current interaction in water Cherenkov
detectors. In the excitation-energy region of the s-hole state between 16 MeV
and 40 MeV in 15N, the branching ratio of emitting gamma-rays with the energies
at more-than-6 MeV are found to be 15.6+-1.3+0.6-1.0%. Taking into account the
spectroscopic factor of the s-hole state, the total emission probability is
found to be 3.1%. This is about 1/10 compared with the emission probability of
the 6.32 MeV gamma-ray from the 3/2- p-hole state in 15N. Moreover, we searched
for a 15.1 MeV gamma-ray from the 12C 1+ state which may be populated after the
particle-decay of the s-hole state in 15N. Such a high energy gamma-ray from
the hole state would provide a new method to search for mode-independent
nucleon decay even if the emission probability is small. No significant signal
is found within a statistical uncertainty.
