2022/07/06 by Crivellin, Andreas
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #Nuclear Experiment (nucl-ex) #Nuclear Theory (nucl-th)
paper · doi:10.48550/arxiv.2207.02507
The determinations of the Cabibbo angle from kaon, pion, D and tau decays disagree with the one from super-allowed beta decays. The resulting ≈ 3 σ deficit in first row (but also first column) CKM unitarity is known as the Cabibbo angle anomaly (CAA). Determining Vud from beta decays requires knowledge of the Fermi constant GF, usually extracted from muon decay. However, because new physics might also affect muon decay, and thus the determination of the Fermi constant, an interesting interplay with the global electroweak fit arises where GF is a crucial input. In these proceedings we review the CAA and its different interpretations in terms of physics beyond the SM, first discussing the corresponding effect in the effective field theory and then using (simplified) models.