相关论文: Theoretical point of view on Cabibbo angle anomaly
The determinations of the Cabibbo angle from kaon, pion, $D$ and tau decays disagree with the one from super-allowed beta decays. The resulting $\approx 3\,\sigma$ deficit in first row (but also first column) CKM unitarity is known as the…
A modified neutrino sector could imprint a signature on precision measurements of the quark sector because many such measurements rely on the semi-leptonic decays of the charged currents. Currently, global fits of the determinations of the…
The Cabibbo-Cobayashi-Maskawa (CKM) matrix parametrizes the misalignement between the up- and down-quark mass basis in the Standard Model (SM). The observation of first row CKM unitarity violation has recently emerged as a new anomaly of…
The combination of precise determinations of $V_{us}$ and $V_{ud}$ hints towards a violation of the CKM first row unitarity at about $3\sigma$ level. Conversely, the recent measurement of the $W$-boson mass by the CDF Collaboration exhibits…
The most recent determinations of $V_{ud}$ from superallowed beta decays lead to a discrepancy when compared to the value implied by mesonic CKM measurements combined with CKM unitarity. On top of this, improved precision in lattice QCD…
The Cabibbo Angle Anomaly, an apparent deficit in first-row CKM unitarity, can be addressed by leptophilic Standard Model extensions that generate new contributions to the Fermi constant and affect the determination of the CKM element…
Due to a recent more precise evaluation of $V_{ud}$ and $V_{us}$, the unitarity condition of the first row in the Cabibbo-Kobayashi-Maskawa (CKM) matrix: $|V_{ud}|^2 + |V_{us}|^2 + |V_{ub}|^2 = 0.99798 \pm 0.00038$ now stands at a deviation…
We point out that testing the equality of the Cabibbo angle as extracted from $\Gamma(K\rightarrow \pi l\nu)$, the ratio $\Gamma(K\rightarrow l\nu)/\Gamma(\pi\rightarrow l\nu)$ and nuclear $\beta$ decays is not identical to a test of first…
New developments in both the theories and experiments related to the extraction of the top-row Cabibbo-Kobayashi-Maskawa matrix elements $V_{ud}$ and $V_{us}$ led to a series of new anomalies, for instance the apparent violation of the…
Recent developments in the Standard Model analysis of semileptonic charged-current processes involving light quarks have revealed $\sim 3\sigma$ tensions in Cabibbo universality tests involving meson, neutron, and nuclear beta decays. In…
We review the recent experimental and theoretical progress in the determination of |V_{ud}| and |V_{us}|, and the status of the most stringent test of CKM unitarity. Future prospects on |V_{cd}| and |V_{cs}| are also briefly discussed.
The first row of the Cabibbo-Cobayashi-Maskawa (CKM) matrix shows a discrepancy of $\sim $$3\,\sigma$ with unitarity, known as the "Cabibbo Angle Anomaly" (CAA). This tension can be explained via modified $W$ couplings to leptons, but in…
It is pointed out that the recent measurement of the angle $\gamma$ of the unitarity triangle, providing irrefutable evidence for a complex Cabibbo-Kobayashi-Maskawa (CKM) matrix, presents a great challenge for supersymmetric models with…
After the recent high precision determinations of $V_{us}$ and $V_{ud}$, the first row of the CKM matrix shows more than $4\sigma$ deviation from unitarity. Two possible scenarios beyond the Standard Model can be investigated in order to…
Typically in unified theories the neutrino mixing angles, like the Cabibbo-Kobayashi-Maskawa (CKM) angles of the quarks, are related to the small mass ratios between fermions of different generations and are therefore quite small. A new…
There are two tensions related to the Cabibbo angle of the CKM matrix. First, the determinations of $V_{us}$ from $K_{\mu 2}$, $K_{\ell3}$, and $\tau$ decays disagree at the $3\sigma$ level. Second, using the average of these results in…
Hadronic tau decays provide several ways to extract the Cabbibo-Kobashi-Maskawa (CKM) matrix element V_{us}. The most precise determination involves using inclusive tau decays and requires as input the total branching ratio into strange…
Arguments coming from Quantum Field Theory are supplemented with a 1-loop perturbative calculation to settle the non-unitarity of mixing matrices linking renormalized mass eigenstates to bare flavor states for non-degenerate coupled…
We point out that hints of deviations from unitarity in the first row of the CKM matrix may be explained by the presence of a single vector-like top. We study how the stringent experimental constraints arising from CP Violation in the kaon…
We present a supersymmetric standard model with three gauged Abelian symmetries, of a type commonly found in superstrings. One is anomalous, the other two are $E_6$ family symmetries. It has a vacuum in which only these symmetries are…