High precision in CKM unitarity tests in $b$ and $c$ decays

Lenz, Alexander; Monteil, S.

doi:10.48550/arxiv.2207.11055

Cited by 2 publications

(2 citation statements)

References 62 publications

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“…The determination of the CKM parameters exclusively from tree-level decays could in principle reduce the depen-dence of CKM parameters on NP 12 and the prospects of their determination in the coming years are good [99]. However, the present tensions between inclusive and exclusive determination of |V cb | is a stumbling block on this route to SM predictions of branching ratios that are very sensitive to |V cb | [30].…”

Section: Discussionmentioning

confidence: 99%

Standard Model predictions for rare K and B decays without new physics infection

Buras

2023

Eur. Phys. J. C

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The Standard Model (SM) does not contain by definition any new physics (NP) contributions to any observable but contains four CKM parameters which are not predicted by this model. We point out that if these four parameters are determined in a global fit which includes processes that are infected by NP and therefore by sources outside the SM, the resulting so-called SM contributions to rare decay branching ratios cannot be considered as genuine SM contributions to the latter. On the other hand genuine SM predictions, that are free from the CKM dependence, can be obtained for suitable ratios of the K and B rare decay branching ratios to $$\Delta M_s$$ Δ M s , $$\Delta M_d$$ Δ M d and $$|\varepsilon _K|$$ | ε K | , all calculated within the SM. These three observables contain by now only small hadronic uncertainties and are already well measured so that rather precise SM predictions for the ratios in question can be obtained. In this context the rapid test of NP infection in the $$\Delta F=2$$ Δ F = 2 sector is provided by a $$|V_{cb}|-\gamma $$ | V cb | - γ plot that involves $$\Delta M_s$$ Δ M s , $$\Delta M_d$$ Δ M d , $$|\varepsilon _K|$$ | ε K | , and the mixing induced CP-asymmetry $$S_{\psi K_S}$$ S ψ K S . As with the present hadronic matrix elements this test turns out to be negative, assuming negligible NP infection in the $$\Delta F=2$$ Δ F = 2 sector and setting the values of these four observables to the experimental ones, allows to obtain SM predictions for all K and B rare decay branching ratios that are most accurate to date and as a byproduct to obtain the full CKM matrix on the basis of $$\Delta F=2$$ Δ F = 2 transitions alone. Using this strategy we obtain SM predictions for 26 branching ratios for rare semileptonic and leptonic K and B decays with the $$\mu ^+\mu ^-$$ μ + μ - pair or the $$\nu {\bar{\nu }}$$ ν ν ¯ pair in the final state. Most interesting turn out to be the anomalies in the low $$q^2$$ q 2 bin in $$B^+\rightarrow K^+\mu ^+\mu ^-$$ B + → K + μ + μ - ($$5.1\sigma $$ 5.1 σ ) and $$B_s\rightarrow \phi \mu ^+\mu ^-$$ B s → ϕ μ + μ - ($$4.8\sigma $$ 4.8 σ ).

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Section: Discussionmentioning

confidence: 99%

Standard Model predictions for rare K and B decays without new physics infection

Buras

2023

Eur. Phys. J. C

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“…However, they might be feasible for the flavour physics programme at the high luminosity upgrade of the LHC [140] or even further in the future at FCC-ee, see e.g. [141,142].…”

Section: Jhep04(2023)034mentioning

confidence: 99%

Quark-hadron duality at work: lifetimes of bottom baryons

Gratrex

Lenz

Melić

et al. 2023

J. High Energ. Phys.

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In the 1990s, very low experimental values for the lifetime ratio τ(Λb)/τ(Bd) triggered a considerable amount of doubt in the applicability of the heavy quark expansion (HQE), which is based on the assumption of quark-hadron duality (QHD) for inclusive total decay rates. However, these low values turned out to be the result of purely experimental problems, and the current HFLAV average reads τ(Λb)/τ(Bd) = 0.969(6). In this work, we present the Standard Model predictions for the b-baryon lifetimes within the framework of the HQE. In particular, we include for the first time the contribution of the Darwin term and we update the estimates for the matrix elements of the dimension-six four-quark operators. Within experimental and theoretical uncertainties, we find excellent agreement between the data and the HQE predictions, and thus no indication for any visible violation of QHD. Our numerical results can be summarised by the ratios τ(Λb)/τ(Bd) = 0.955(14), $$ \tau \left({\varOmega}_b^{-}\right) $$ τ Ω b − /τ(Bd) = 1.081(42), and $$ \tau \left({\Xi}_b^0\right)/\tau \left({\Xi}_b^{-}\right) $$ τ Ξ b 0 / τ Ξ b − = 0.929(28).

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High precision in CKM unitarity tests in $b$ and $c$ decays

Cited by 2 publications

References 62 publications

Standard Model predictions for rare K and B decays without new physics infection

Standard Model predictions for rare K and B decays without new physics infection

Quark-hadron duality at work: lifetimes of bottom baryons

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