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Neutron beta decay and the current determination of Vud

A. Garcia·J. L. Garcia-Luna·G. Lopez Castro
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Abstract

Measurements of neutron beta decay observables required to determine $|V_{ud}|$ are reaching the 0.1% accuracy. In this paper we review the calculation of the decay rate of this process, discuss its relevant uncertainties, and obtain an expression that is precise at the $10^{-4}$ level. Our analysis clearly shows the necessity of measurements of $λ$, the ratio of axial/vector couplings. The current situation in neutron beta decay is that one cannot yet quote a single consistent value for $|V_{ud}|$ from it. We also discuss the region of parameter space in the $|V_{ud}|$--$λ$ plane where new physics effects should lie, if they contribute to neutron beta decay.

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A. Garcia, J. L. Garcia-Luna, G. Lopez Castro. 2000-06-19. Neutron beta decay and the current determination of Vud. https://doi.org/10.1016/s0370-2693(01)00051-x

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