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Description
Precision measurements of free neutron decay provide a powerful probe of the Standard Model and potential physics beyond it (BSM). Experiments such as PERKEO III and PERC are designed to study neutron beta decay with unprecedented accuracy by analyzing correlations among decay products.
PERKEO III has delivered the most precise measurement of the beta asymmetry parameter A, from which the most precise determination of λ is obtained. Being this ratio between the axial-vector and vector coupling constants (λ=g_A/g_V), λ plays a key role in determining the Cabbibo-Kobayashi-Maskawa (CKM) matrix element V_{ud} and thus in testing its unitarity.
While PERC is designed to further improve this precision, it is still under construction. In the meantime, existing results can be further refined by reanalyzing the data with improved theoretical corrections and by achieving a better understanding of the dominant sources of systematic uncertainty.