Measurement of gamma-ray production via neutron-$^{16}$O reaction using a 77 MeV quasi-mono energetic neutron beam.

Understanding of gamma-ray production via neutron interactions on oxygen is essential for the study of neutrino neutral-current elastic interactions in water Cherenkov detectors. A measurement of gamma-ray production from such reactions was performed using a 77 MeV quasi-mono energetic neutron beam. Several gamma-ray peaks, which are expected to come from neutron-$^{16}$O reactions, are observed and cross sections are measured for three gamma-ray components, 6.13 MeV from $^{16}$O($3^{-}$), 5.27 MeV from $^{15}$N($\frac{5}{2}^{+}$), and 4.44 MeV from $^{12}$C($2^{+}$). The results are $\sigma_{\gamma({\rm 6.13 \ MeV})} = {\rm 4.2 \pm 0.1 (stat.) \pm 0.9 (syst.) \ mb}$, $\sigma_{\gamma({\rm 5.27 \ MeV})} = {\rm 6.4 \pm 0.1 (stat.) \pm 2.2 (syst.) \ mb}$, and $\sigma_{\gamma({\rm 4.44 \ MeV})} = {\rm 8.3 \pm 0.1 (stat.) \pm 1.6 (syst.) \ mb}$, respectively. These are the first measurement results at the corresponding neutron energy with use of a mono energy beam.