Experimental Search for Neutron to Mirror Neutron Oscillations as an Explanation of the Neutron Lifetime Anomaly

TL;DR

This study tested whether neutron to mirror neutron oscillations could explain the neutron lifetime discrepancy but found no supporting evidence, thereby ruling out this hypothesis as the cause.

Contribution

The paper presents an experimental search for neutron to mirror neutron oscillations in a high magnetic field to address the neutron lifetime anomaly.

Findings

Excluded the mirror neutron oscillation explanation for the neutron lifetime discrepancy.

Performed a sensitive search at the Spallation Neutron Source with a 6.6 T magnetic field.

Provided constraints on neutron to mirror neutron conversion probabilities.

Abstract

An unexplained $>4\,\sigma$ discrepancy persists between "beam" and "bottle" measurements of the neutron lifetime. A new model proposed that conversions of neutrons $n$ into mirror neutrons $n'$, part of a dark mirror sector, can increase the apparent neutron lifetime by $1\%$ via a small mass splitting $\Delta{m}$ between $n$ and $n'$ inside the 4.6 T magnetic field of the National Institute of Standards and Technology Beam Lifetime experiment. A search for neutron conversions in a 6.6 T magnetic field was performed at the Spallation Neutron Source which excludes this explanation for the neutron lifetime discrepancy.