Cross section for supernova axion observation in neutrino water Čherenkov detectors
Pierluca Carenza, G. Co’, Maurizio Giannotti, Alessandro Lella, Giuseppe Lucente, Alessandro Mirizzi, T. Rauscher
Abstract
Axions coupled to nucleons might be copiously emitted from core-collapse supernovae (SNe). If the axion-nucleon coupling is strong enough, then axions would be emitted from the SN as a burst and, reaching Earth, may excite the oxygen nuclei in water \ifmmode \check{C}\else \v{C}\fi{}herenkov detectors ($^{16}\mathrm{O}+a\ensuremath{\rightarrow}^{16}\mathrm{O}^{*}$). This process will be followed by decay(s) of the excited state resulting in an emission of photons and thus providing a possibility for a direct detection of axions from a galactic SN in large underground neutrino \ifmmode \check{C}\else \v{C}\fi{}herenkov detectors. Motivated by this possibility, we present an updated calculation of axion-oxygen cross section obtained by using self-consistent continuum random-phase approximation. We calculate the branching ratio of the oxygen nucleus deexcitation into $\ensuremath{\gamma}$ rays, neutrons, protons, and $\ensuremath{\alpha}$ particles and also consider photon emission from secondary nuclei to compute a total $\ensuremath{\gamma}$ spectrum created when axions excite $^{16}\mathrm{O}$. These results are used to revisit the detectability of axions from SN 1987A in Kamiokande-II.