High precision measurements of isospin T = 1/2 decays in the neutron and nuclei provide strong model-independent constraints on extensions to the standard model of particle physics. A measurement of the β-asymmetry in 19Ne decay between the initial nuclear spin and the direction of the emitted positron is presented which establishes this decay as the most precisely characterized nuclear mirror and fixes the Fermi-to-Gamow-Teller mixing ratio to ρ = 1.6014(+21/ − 28)sys(08)stat. This is consistent with the previous, most precise measurement (1), produces a value of the CKM unitarity parameter Vud in agreement with the nuclear mirror, neutron and superallowed β-decay data sets, shows no evidence for second class currents, and can be effectively used with neutron decay data to place a limits on exotic tensor couplings.
|Original language||English (US)|
|State||Published - Sep 28 2020|
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