Search for Tri-Nucleon Decay in the Majorana Demonstrator

Author(s): Alvis, SI; Arnquist, IJ; III, FT Avignone; Barabash, AS; Barton, CJ; Bertrand, FE; Bos, B; Brudanin, V; Busch, M; Buuck, M; Caldwell, TS; Chan, Y-D; Christofferson, CD; Chu, P-H; Cuesta, C; Detwiler, JA; Efremenko, Yu; Ejiri, H; Elliott, SR; Gilliss, T; Giovanetti, GK; Green, MP; Gruszko, J; Guinn, IS; Guiseppe, VE; Haufe, CR; Hegedus, RJ; Hehn, L; Henning, R; Aguilar, D Hervas; Hoppe, EW; Howe, MA; Keeter, KJ; Kidd, MF; Konovalov, SI; Kouzes, RT; Lopez, AM; Martin, RD; Massarczyk, R; Meijer, SJ; Mertens, S; Myslik, J; Othman, G; Pettus, W; Piliounis, A; Poon, AWP; Radford, DC; Rager, J; Reine, AL; Rielage, K; Ruof, NW; Shanks, B; Shirchenko, M; Tedeschi, D; Varner, RL; Vasilyev, S; Vasundhara; White, BR; Wilkerson, JF; Wiseman, C; Xu, W; Yakushev, E; Yu, C-H; Yumatov, V; Zhitnikov, I; Zhu, BX | Abstract: 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 $4.7\times10^{25}$ yr for the decay $^{76}{\rm Ge(ppp)} \to ^{73}{\rm Cu}\ e^+\pi^+\pi^+$. The half-life limit for the invisible tri-proton decay mode of $^{76}$Ge was found to be $7.5\times10^{24}$ yr.