Full $K_{\ell 3}$ radiative corrections and implications on $|V_{us}|$

Seng, Chien-Yeah; Galviz, Daniel; Gorchtein, Mikhail; Meißner, Ulf-G.

doi:10.48550/arxiv.2203.05217

Cited by 4 publications

(6 citation statements)

References 32 publications

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“…With the strategies above, Refs. 18,19,20 updated the theory predictions of long-distance EMRC to all channels in K 3 decays, see Table 1. The main sources of theory uncertainty in the new determination are: (1) Contributions from inelastic (inel) states to I λ A , (2) Lattice (lat) uncertainty in < γW , (3) Uncertainty due to non-forward (NF) effects in the γW -box diagram, (4) Higher-order (O(e 2 p 4 )) ChPT corrections and, (5) The poorly-determined LECs in δf − .…”

Section: Rc In Kaon Semileptonic Decaysmentioning

confidence: 91%

“…With its success in neutron, Sirlin's representation was later applied to study the RC in K 3 decays, i.e. K → π + ν(γ), which are crucial in the extraction of V us 15,16,17,18,19,20 . It is more complicated than the free neutron RC due to several reasons: (1) Unlike neutron, many terms in Sirlin's representation either do not vanish, or are not saturated by the convection terms contribution; and (2) the forward limit cannot be simply taken because the kaon and pion momenta are very different.…”

Section: Rc In Kaon Semileptonic Decaysmentioning

confidence: 99%

“…This leads us to the following simple strategy: On the one hand, one may calculate δf + with fully non-perturbative methods based on Sirlin's representation; on the other hand, for δf − which is only relevant to K µ3 , one may split it into infrared (IR)-singular and IR-regular pieces, the former is calculated non-perturbatively and the latter perturbatively. Based on this strategy, a re-analysis was performed first to the RC in K e3 decays 18,19 and later in K µ3 20 , which we briefly describe as follows. We start from δf + which are computed non-perturbatively:…”

Section: Rc In Kaon Semileptonic Decaysmentioning

confidence: 99%

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New calculations of neutron and kaon decays

Seng¹

2022

Preprint

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We describe two recent developments of the radiative correction theory in semileptonic beta decays. For neutron, a novel dispersive analysis of the γW -box diagram making use of neutrino scattering data leads to an improved precision and a shifted central value of V ud ; for kaon, an appropriate combination of meson form factors, lattice QCD inputs and chiral perturbation theory gives a much-improved determination of the radiative corrections in semileptonic kaon decays. These new calculations help to unveil/sharpen a series of anomalies in the measurements of V ud and Vus that may point towards the existence of new physics.

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Section: Rc In Kaon Semileptonic Decaysmentioning

confidence: 91%

Section: Rc In Kaon Semileptonic Decaysmentioning

confidence: 99%

Section: Rc In Kaon Semileptonic Decaysmentioning

confidence: 99%

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New calculations of neutron and kaon decays

Seng¹

2022

Preprint

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“…Note that the results of Kl3 and Kµ2 differ by 3 standard deviations, see e.g. [65]. For testing unitarity of the first row the uncertainties in V ub are irrelevant.…”

Section: Cabibbo Anomalymentioning

confidence: 99%

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

Lenz¹,

Monteil²

2022

Preprint

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This article surveys the important questions attached to unitarity tests of the Cabibbo-Kobayashi-Maskawa matrix, with a focus on the direct determinations of the magnitude of CKM matrix elements. The current CKM anomalies are discussed and the clear-cut prospects at LHCb and Belle II envisaged. The anticipated precision on CP -conserving and CP -violating observables at the projected upgrades of the LHCb and Belle II experiments is examined from the point of view of the search for New Physics in B-meson mixing, addressing the bottlenecks in precision for the interpretation of the measurements for future experiments and highlighting the related theoretical and experimental challenges. The vibrant prospects at future e + e − colliders running at the Z 0 pole and W + W − are eventually discussed.

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“…The additional fourth error comes from the experimental value. When an updated value of f + (0)|V us | = 0.21635(39) [36] is employed, the obtained value is not largely changed as |V us | = 0.22501(24)( +6 −109 )(11)(41).…”

mentioning

confidence: 99%

$K_{\ell 3}$ form factors at the physical point towards the continuum limit

Ishikawa,

Ishizuka,

Kuramashi

et al. 2022

Preprint

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We present updated results for the form factors of the kaon semileptonic (K ℓ3 ) decay process calculated with N f = 2 + 1 nonperturbatively O(a)-improved Wilson quark action and Iwasaki gauge action at the physical point on large volumes of more than (10 fm) 4 . In addition to our previous calculation at the lattice spacing a = 0.085 fm, we perform a calculation at the second lattice spacing of 0.063 fm. Using the results for the form factors extracted from 3-point functions with the local and also conserved vector currents at the two lattice spacings, continuum extrapolation and interpolation of the momentum transfer are carried out simultaneously to obtain the value of the form factor f + (0) at the zero momentum transfer in the continuum limit. After investigation of stability of f + (0) against several fit forms and different data, we obtain f + (0) = 0.9615(10)( +47 −2 )( 5), where the first, second, and third errors are statistical, systematic errors from choice of the fit forms and isospin breaking effect, respectively. Furthermore, we obtain the slope and curvature of the form factors, and the phase space integral from the momentum transfer dependence of the form factors. Combining our value of f + (0) and experimental input of the K ℓ3 decay, one of the Cabibbo-Kobayashi-Maskawa matrix elements |V us | is determined as |V us | = 0.2252( +5 −12 ), whose error contains the experimental one as well as that in the lattice calculation. This value is reasonably consistent with the ones determined from recent lattice QCD results of f + (0) and also the one determined through the kaon leptonic decay process. We observe some tension between our value and |V us | evaluated from the unitarity of the CKM matrix with |V ud |, while it depends on the size of the error of |V ud |. It is also found that |V us | determined with our phase space integrals through six K ℓ3 decay processes is consistent with the above one using f + (0).

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Full $K_{\ell 3}$ radiative corrections and implications on $|V_{us}|$

Cited by 4 publications

References 32 publications

New calculations of neutron and kaon decays

New calculations of neutron and kaon decays

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

$K_{\ell 3}$ form factors at the physical point towards the continuum limit

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