Determination of the Weak Axial Vector Coupling from a Measurement of the Beta-Asymmetry Parameter A in Neutron Beta Decay

Abstract

We report on a new measurement of the neutron beta-asymmetry parameter $A$ with the instrument \perkeo. Main advancements are the high neutron polarization of $P=99.7(1)$ from a novel arrangement of super mirror polarizers and reduced background from improvements in beam line and shielding. Leading corrections were thus reduced by a factor of 4, pushing them below the level of statistical error and resulting in a significant reduction of systematic uncertainty compared to our previous experiments. From the result $A_0=-0.11996(58)$, we derive the ratio of the axial-vector to the vector coupling constant $\hat{I}»=g_{\mathrm{A}}/g_{\mathrm{V}}=-1.2767(16)$

5 pages, 4 figures