New limits on Bosonic Dark Matter, Solar Axions, Pauli Exclusion Principle Violation, and Electron Decay from the Majorana Demonstrator

We present new limits on exotic keV-scale physics based on 478 kg d of MAJORANA DEMONSTRATOR commissioning data. Constraints at the 90% confidence level are derived on bosonic dark matter (DM) and solar axion couplings, Pauli exclusion principle violating (PEPV) decay, and electron decay using monoenergetic peak signal-limits above our background. Our most stringent DM constraints are set for 11.8 keV mass particles, limiting $g_{Ae} <4.5\times 10^{-13}$ for pseudoscalars and $\frac{\alpha'}{\alpha} < 9.7\times 10^{-28}$ for vectors. We also report a 14.4 keV solar axion coupling limit of $g_{AN}^{\mathrm{eff}}\times g_{Ae}~<~3.8 \times 10^{-17}$, a $\frac{1}{2}\beta^2~<~8.5\times10^{-48}$ limit on the strength of PEPV electron transitions, and a lower limit on the electron lifetime of $\tau_e > 1.2 \times 10^{24}\;$yr for $e^- \rightarrow$ invisible.