Fill and dump measurement of the neutron lifetime using an asymmetric magneto-gravitational trap

TL;DR

This paper reports a new neutron lifetime measurement using an asymmetric magneto-gravitational trap and the fill and dump method, contributing to resolving discrepancies among previous measurements.

Contribution

It introduces a novel measurement technique with external neutron counting in an asymmetric trap, providing an independent check on existing neutron lifetime results.

Findings

The measured neutron lifetime is consistent with previous in situ measurements.

The new method offers an alternative approach to neutron lifetime determination.

Results support the existence of systematic differences in prior measurements.

Abstract

The past two decades have yielded several new measurements and reanalyses of older measurements of the neutron lifetime. These have led to a 4.4 standard deviation discrepancy between the most precise measurements of the neutron decay rate producing protons in cold neutron beams and the lifetime measured in neutron storage experiments. Measurements using different techniques are important for investigating whether there are unidentified systematic effects in any of the measurements. In this paper we report a new measurement using the Los Alamos asymmetric magneto-gravitational trap where the surviving neutrons are counted external to the trap using the fill and dump method. The new measurement gives a free neutron lifetime of . Although this measurement is not as precise, it is in statistical agreement with previous results using in situ counting in the same apparatus.