# Constraints on the Dark Matter Interpretation $n \rightarrow \chi + e^+ e^-$ of the Neutron Decay Anomaly with the PERKEO II experiment

## TL;DR

This paper uses data from the PERKEO II experiment to constrain the dark matter decay mode of the neutron, specifically the decay into a dark matter particle and an electron-positron pair, addressing the neutron lifetime discrepancy.

## Contribution

It provides experimental limits on the neutron's dark decay mode, excluding a 1% branching fraction for most of the dark matter particle mass range.

## Key findings

- Excluded a 1% decay branching fraction for neutron dark decay in most mass ranges.
- Set upper limits on the dark decay mode using PERKEO II data.
- Contributed to resolving the neutron lifetime discrepancy by constraining dark decay channels.

## Abstract

Discrepancies from in-beam and in-bottle type experiments measuring the neutron lifetime are on the 4$\sigma$ standard deviation level. In a recent publication Fornal and Grinstein proposed that the puzzle could be solved if the neutron would decay on the one percent level via a dark decay mode, one possible branch being $n \rightarrow \chi + e^+ e^-$. With data from the \perkeoII experiment we set limits on the branching fraction and exclude a one percent contribution for $95\,\%$ of the allowed mass range for the dark matter particle.