Search for trinucleon decay in the Majorana Demonstrator

Abstract

The Majorana Demonstrator is an ultra-low-background experiment searching for neutrinoless double-beta decay in $^{76}\mathrm{Ge}$. The heavily shielded array of germanium detectors, placed nearly a mile underground at the Sanford Underground Research Facility in Lead, South Dakota, also allows searches for new exotic physics. We present the first limits for trinucleon decay-specific modes and invisible decay modes for Ge isotopes. We find a half-life limit of $4.9\ifmmode\times\else\texttimes\fi{}{10}^{25}\text{ }\text{ }\mathrm{yr}$ for the decay $^{76}\mathrm{Ge}(\mathrm{ppn})\ensuremath{\rightarrow}^{73}\mathrm{Zn}$ ${e}^{+}{\ensuremath{\pi}}^{+}$ and $4.7\ifmmode\times\else\texttimes\fi{}{10}^{25}\text{ }\text{ }\mathrm{yr}$ for the decay $^{76}\mathrm{Ge}(\mathrm{ppp})\ensuremath{\rightarrow}^{73}\mathrm{Cu}$ ${e}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}$. The half-life limit for the invisible triproton decay mode of $^{76}\mathrm{Ge}$ was found to be $7.5\ifmmode\times\else\texttimes\fi{}{10}^{24}\text{ }\text{ }\mathrm{yr}$.