Combined Explanation of the Z→bb[over ¯] Forward-Backward Asymmetry, the Cabibbo Angle Anomaly, and τ→μνν and b→sℓ^{+}ℓ^{-} Data

Radiative Corrections to Superallowed β Decays in Effective Field Theory

The accuracy of V_{ud} determinations from superallowed β decays critically hinges on control over radiative corrections. Recently, substantial progress has been made on the single-nucleon, universal corrections, while nucleus-dependent effects, typically parametrized by a quantity δ_{NS}, are much less well constrained. Here, we lay out a program to evaluate this correction from effective field theory (EFT), highlighting the dominant terms as predicted by the EFT power counting. Moreover, we compare the results to a dispersive representation of δ_{NS} and show that the expected momentum scaling applies even in the case of low-lying intermediate states. Our EFT framework paves the way toward ab initio calculations of δ_{NS} and thereby addresses the dominant uncertainty in V_{ud}.

Round table on Standard Model Anomalies

This contribution to “The XVth Quark confinement and the Hadron spectrum conference" covers a description, both theoretical and experimental, of the present status of a set of very different anomalies. The discussion ranges from the long standing b → sℓℓ anomalies, (g − 2) and the new MW anomaly.

Fermi Constant from Muon Decay Versus Electroweak Fits and Cabibbo-Kobayashi-Maskawa Unitarity

The Fermi constant G_{F} is extremely well measured through the muon lifetime, defining one of the key fundamental parameters in the standard model (SM). Therefore, to search for physics beyond the SM (BSM) via G_{F}, the constraining power is determined by the precision of the second-best independent determination of G_{F}. The best alternative extractions of G_{F} proceed either via the global electroweak (EW) fit or from superallowed β decays in combination with the Cabibbo angle measured in kaon, τ, or D decays. Both variants display some tension with G_{F} from muon decay, albeit in opposite directions, reflecting the known tensions within the EW fit and hints for the apparent violation of Cabibbo-Kobayashi-Maskawa unitarity, respectively. We investigate how BSM physics could bring the three determinations of G_{F} into agreement using SM effective field theory and comment on future perspectives.

Minimal Explanation of Flavor Anomalies: B-Meson Decays, Muon Magnetic Moment, and the Cabibbo Angle

Significant deviations from the standard model are observed in semileptonic charged and neutral-current B decays, the muon magnetic moment, and the extraction of the Cabibbo angle. We propose that these deviations point towards a coherent pattern of new physics effects induced by two scalar mediators, a leptoquark S_{1} and a charged singlet ϕ^{+}. While S_{1} can provide solutions to charged-current B decays and the muon magnetic moment, and ϕ^{+} can accommodate the Cabibbo-angle anomaly independently, their one-loop level synergy can also address neutral-current B decays. This framework provides the most minimal explanation to the above-mentioned anomalies, while being consistent with all other phenomenological constraints.

Anomalous Zbb[over ¯] Couplings: From LEP to LHC

The bottom quark forward-backward asymmetry (A_{FB}^{b}) data at LEP exhibits a long-standing discrepancy with the standard model prediction. We propose a novel method to probe the Zbb[over ¯] interactions through gg→Zh production at the LHC, which is sensitive to the axial-vector component of the Zbb[over ¯] couplings. The apparent degeneracy of the anomalous Zbb[over ¯] couplings implied by the LEP precision electroweak measurements seems to be resolved by the current 13 TeV LHC Zh data, which is, however, dominated by the two data points with high transverse momentum of Z boson whose central values are in conflict with the standard model prediction. We also show the potential of the HL-LHC to either verify or exclude the anomalous Zbb[over ¯] couplings observed at LEP through measuring the Zh production rate at the HL-LHC, and this conclusion is not sensitive to the possible new physics contribution induced by top quark or Higgs boson anomalous couplings in the loop.