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Misha Gorshteyn: Cabibbo unitarity: anomaly (dis)appears
June 19 at 15:30 - 16:30
Unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix is one of the cornerstones of the Standard Model.
The unitarity constraint that involves the top-row matrix elements, $|V_{ud}|^2+|V_{us}|^2+|V_{ub}|^2=1$ is particularly
important because all elements are measured very precisely permitting a test at the 0.01% level. At this accuracy,
$V_{ub}sim10^{-3}$ is irrelevant, and the unitarity constraint reduces to the two-flavor Cabibbo unitarity pattern with a single
Cabibbo angle $theta_C$ and $V_{ud}=costheta_C$ and $V_{us}$. At present, a mild deficit is observed,
$|V_{ud}|^2+|V_{us}|^2=0.9985(7)$. As such, this deficit may suggest some new physics, but to make this claim all Standard
Model ingredients must be firmly under control. I review these ingredients across theory and experiment and review the most
recent developments.
https://indico.ijs.si/event/2861/