Search for Tri-Nucleon Decay in the Majorana Demonstrator

The Majorana Demonstrator is an 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. The conservation of the baryons number is an empirical symmetry of the Standard Model. Since its violation is one of the requirements to explain the matter-antimatter asymmetry of the Universe, baryon number violation has been searched for in a variety of nuclear decay modes. One theory with an anomaly-free Z6 symmetry allows tri-nucleon decay while single- or double-nucleon decay processes are forbidden. We present the first limits for tri-nucleon decay-specific modes and invisible decay modes for Ge isotopes. The half-life limit was 4.9e25 yr for the decay 76Ge(ppn)->73Zn e+ pi+ and 4.7e25 yr for the decay 76Ge(ppp)->73Cu e+ pi+ pi+. The half-life limit was 7.5e24 yr for the invisible tri-proton decay mode of 76Ge.