Laboratory for Particle Physics (LTP)

LTP Colloquium

Cabibbo Angle Anomaly: Status and Outlook

Thursday, May 2, 2024, 16:00

Mikhail Gorshteyn, Mainz University

Unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix is a mathematical expression of universality of the weak interaction across lepton and quark sectors, as well as the Standard Model's completeness. The most precisely measured top-row elements warrant Standard Model tests at the 0.01% level. At this precision, the contribution of Vub is negligible, leaving one with the simple Cabibbo unitarity pattern, |Vud|=cosθC, |Vus|=sinθC. Combining kaon decays with nuclear beta decays, currently a 2.5σ deficit is observed. This deficit, also coined the Cabibbo angle anomaly, relies on a body of high-precision experimental measurements and theoretical calculations. I give an overview of the recent developments in the SM theory of beta decays of free and bound neutrons, and kaons. I discuss future steps, as well as possible implications for BSM searches at low energies.