Search for charge nonconservation and Pauli exclusion principle violation with the Majorana Demonstrator

TL;DR

This paper reports high-precision tests for violations of charge conservation and the Pauli exclusion principle using germanium detectors, setting new limits on electron decay and quantum state violations, which could indicate new physics beyond the standard model.

Contribution

The study provides the first experimental limits on charge nonconservation and Pauli principle violations using the Majorana Demonstrator, improving previous bounds significantly.

Findings

Lower limit on electron lifetime for decay channel improved by over an order of magnitude.

Set new limits on the probability of electrons being in symmetric quantum states.

No evidence found for violations, constraining new physics models.

Abstract

Charge conservation and the Pauli exclusion principle result from fundamental symmetries in the standard model of particle physics, and are typically taken as axiomatic. High-precision tests for small violations of these symmetries could point to new physics. Here we consider three models for violation of these processes, which would produce detectable ionization in the high-purity germanium detectors of the \MJD\ experiment. Using a 37.5 kg-yr exposure, we report a lower limit on the electron mean lifetime, improving the previous best limit for the $e \rightarrow \nu_e \overline{\nu_e} \nu_e$ decay channel by more than an order of magnitude. We also present searches for two types of violation of the Pauli exclusion principle, setting limits on the probability of an electron to be found in a symmetric quantum state.