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 ⁷⁶Ge. 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 4.9×10²⁵  yr for the decay ⁷⁶Ge⁢(ppn)→⁷³Zn 𝑒⁺⁢𝜋⁺ and 4.7 ×10²⁵  yr for the decay ⁷⁶Ge⁢(ppp)→⁷³Cu 𝑒⁺⁢𝜋⁺⁢𝜋⁺. The half-life limit for the invisible triproton decay mode of ⁷⁶Ge was found to be 7.5 ×10²⁴  yr.