Search for Tri-Nucleon Decay in the Majorana Demonstrator

The Majorana Demonstrator is an ultra low-background experiment searching for neutrinoless double-beta decay in ${}^{76}$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 tri-nucleon decay-specific modes and invisible decay modes for Ge isotopes. We find a half-life limit of $4.9\times {10}^{25}$ yr for the decay $^{76}{\rm Ge(ppn)} \to {}^{73}{\rm Zn}
e^+\pi^+$and$4.7\times10^{25}$yrforthedecay$^{76}{\rm Ge(ppp)} \to ^{73}{\rm Cu}\ e^+\pi^+\pi^+$. The half-life limit for the invisible tri-proton decay mode of ${}^{76}$Ge was found to be $7.5\times {10}^{24}$ yr.