On the Standard Model Predictions for Rare K and B Decay Branching Ratios: 2022

Buras, Andrzej J.

doi:10.48550/arxiv.2205.01118

Cited by 5 publications

(9 citation statements)

References 19 publications

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“…These are the most precise SM predictions for decays in question to date. In particular in the case of K → πν ν they supersede the widely cited 2015 results [34] 2015), (12) that are clearly out of date as stressed recently in a note by the author [28]. Using our strategy the uncertainties in the two branching ratios have been reduced by a factor of 2.4 and 4.0, respectively.…”

Section: Main Strategy and First Resultssupporting

confidence: 71%

“…This point has been already made in a short note by the present author[28] and very recently in[29] but the solution to this problem suggested in the latter paper is drastically different from the one proposed here that is based on[30,31]. We will comment on it below 3.…”

mentioning

confidence: 61%

“…It is based on the ideas developed in collaboration with Elena Venturini [30,31] and extends them in a significant manner. The short note in [28] by the present author, in which some critical comments about the literature have been made, can be considered as an overture to the present paper. In fact our strategy is consistent with the present pattern of experimental data.…”

Section: Introductionmentioning

confidence: 92%

“…4 As shown recently in [31], the SM predictions for the branching ratios in question and F = 2 observables are drastically different for these two values of |V cb |. This problem existed already in 2015 in the context of the widely cited paper in [34] as stressed recently in a short note in [28]. But this is not the whole story.…”

Section: Introductionmentioning

confidence: 97%

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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: Main Strategy and First Resultssupporting

confidence: 71%

mentioning

confidence: 61%

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 97%

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

Buras

2023

Eur. Phys. J. C

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“…In the SM there are no NP contributions to ∆F = 2 transitions and no assumption on the absence of NP is needed. More on this in [37].…”

Section: Basic Formulaementioning

confidence: 98%

On the Superiority of the $|V_{cb}|-γ$ Plots over the Unitarity Triangle Plots in the 2020s

Buras

2022

Preprint

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The Unitarity Triangle (UT) plots played already for three decades an important role in the tests of the Standard Model (SM) and the determination of the CKM parameters. As of 2022, among the four CKM parameters, |V us | and β are already measured with respectable precision, while this is not the case of |V cb | and γ. In the case of |V cb | the main obstacle are the significant tensions between its inclusive and exclusive determinations from tree-level decays and it could still take some years before a unique value of this parameter will be known. The present uncertainty in γ of 4 • from tree-level decays will be reduced to 1 • by the LHCb and Belle II collaborations in the coming years. Unfortunately in the common UT plots |V cb | is not seen and the experimental improvements in the determination of γ from tree-level decays at the level of a few degrees are difficult to appreciate. In view of these deficiencies of the UT plots with respect to |V cb | and γ and the central role these two CKM parameters will play in this decade, the recently proposed plots of |V cb | versus γ extracted from various processes appear to be superior to the UT plots in the flavour phenomenology of the 2020s. We illustrate this idea with ∆F = 2 observables ∆M s , ∆M d , ε K and with rare decaysIn particular the power of ε K , B(K + → π + ν ν) and B(K L → π 0 ν ν) in the determination of |V cb |, due to their strong dependence on |V cb |, is transparently exhibited in this manner. Combined with future reduced errors on γ and |V cb | from tree-level decays such plots can better exhibit possible inconsistencies between various determinations of these two parameters, caused by new physics, than it is possible with the UT plots. This can already be illustrated on the example of the recently found 2.7σ anomaly in B s → µ + µ − .

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Chiral perturbation theory: reflections on effective theories of the standard model

2023

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The pseudoscalar particles pions, kaons and the g-particle are considerably lighter than the other hadrons such as protons or neutrons. Their lightness was understood as a consequence of approximate chiral symmetry breaking. This led to current algebra, a way to express the relations imposed by the symmetry breaking. It was realized by Weinberg that because of their low mass, it is possible to formulate a purely pionic (effective) field theory at experimental energies, which carries all information on the (non-perturbative) dynamics, symmetries, and their spontaneous breaking of quantum chromodynamics (QCD) and allows for systematic calculations of observables. In this review, we trace these developments and present recent activities in this field. We make the connection to other effective theories, more generally introduced by Wilson, as approximate field theories at low energies. Indeed, principles and paradigms introduced first for pions have become ubiquitous in particle physics and the standard model. Lastly, we turn to the latest development where the present (fundamental) standard model itself is considered as an effective field theory of a-yet to be formulated-even more fundamental theory. We also discuss important techniques that were developed in order to turn chiral perturbation theory into a predictive framework and briefly review some connections between lattice QCD and chiral perturbation theory (ChPT).

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On the Standard Model Predictions for Rare K and B Decay Branching Ratios: 2022

Cited by 5 publications

References 19 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

On the Superiority of the $|V_{cb}|-γ$ Plots over the Unitarity Triangle Plots in the 2020s

Chiral perturbation theory: reflections on effective theories of the standard model

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