Precision Measurement of the Neutron Beta-Decay Asymmetry

TL;DR

This paper reports a highly precise measurement of the neutron beta-decay asymmetry using polarized ultracold neutrons, significantly reducing uncertainties and refining the value of the axial-vector to vector coupling ratio.

Contribution

The study introduces an improved experimental setup and methodology that achieves lower statistical and systematic uncertainties in measuring neutron decay asymmetry.

Findings

Measured asymmetry $A_0 = -0.11954(55)_{stat}(98)_{syst}$

Determined coupling ratio $ ext{lambda} = -1.2756(30)$

Enhanced precision over previous measurements

Abstract

A new measurement of the neutron $\beta$-decay asymmetry $A_0$ has been carried out by the UCNA collaboration using polarized ultracold neutrons (UCN) from the solid deuterium UCN source at the Los Alamos Neutron Science Center (LANSCE). Improvements in the experiment have led to reductions in both statistical and systematic uncertainties leading to $A_0 = -0.11954(55)_{\rm stat.}(98)_{\rm syst.}$, corresponding to the ratio of axial-vector to vector coupling $\lambda \equiv g_A/g_V = -1.2756(30)$.