Branching ratios for deexcitation processes of daughter nuclei following invisible dinucleon decays in ${}^{16}$O

Abstract

Various theories beyond the standard model of particle physics predict the existence of baryon number violating processes resulting in nucleon decay. When occurring within an atomic nucleus, such a decay will be followed by secondary decays of the daughter nucleus unless its ground state is directly populated. In this paper, we estimate branching ratios for processes associated with dinucleon decays of the ${}^{16}$O nucleus. To this end, we use a simple shell model for the ground state of ${}^{16}$O. For decays from the 1$s_{1/2}$ configuration, which result in highly excited states in the daughter nucleus, we employ a statistical model with the Hauser-Feshbach theory. Our analysis indicates that the branching ratio for gamma-ray emission in the energy range between 5 and 9 MeV, which is relevant to low-threshold water Cherenkov experiments such as SNO+, is 4.53%, 35.7%, and 20.2% for the $nn$, $pp$, and $pn$ decays in ${}^{16}$O, respectively. In particular, emission of 6.09 MeV and 7.01 MeV gamma-rays from ${}^{14}$C, and 6.45 MeV and 7.03 MeV gamma-rays from ${}^{14}$N, have branching ratios as large as 10.9%, 20.1%, 7.73% and 8.90%, respectively.

arXiv comment18 pages, 7 figures. To appear in J. of Phys. G

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• Inclusive Nucleon Decay Searches as a Frontier of Baryon Number Violation
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• Benchmarks and applications of the nuclear deexcitation event generator NucDeEx