Standard Model predictions for lepton flavour universality ratios of inclusive semileptonic B decays

Rahimi, Muslem; Vos, Kimberley

doi:10.1007/jhep11(2022)007

Cited by 16 publications

(10 citation statements)

References 43 publications

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“…From the fit, the signal yields are extracted to be 𝑁 𝑋 𝑒𝜈 = 48034 ± 286 and 𝑁 𝑋 𝜇𝜈 = 58569 ± 429 corresponding to an 𝑅(𝑋 𝑒/𝜇 ) value of 𝑅(𝑋 𝑒/𝜇 ) = 1.033 ± 0.010 ± 0.019 (2) where the first uncertainty is statistical and the second systematic. This result agrees with the Standard Model prediction of 1.006 ± 0.001 [14] within 1.3 𝜎 and with a previous measurement from Belle in exclusive 𝐵 → 𝐷 * ℓ𝜈 decays within 0.6 𝜎 [15]. So far, the reported result is the most precise test of 𝑒 − 𝜇 universality in semileptonic 𝐵 decays based on a branching fraction ratio.…”

Section: Henrik Junkerkalefeldsupporting

confidence: 92%

A measurement of the ratio of light-lepton inclusive semileptonic $B$ decay rates $R(X_{e/\mu})$ = $\mathcal{B}(B \rightarrow X e \nu)$ / $\mathcal{B}(B \rightarrow X \mu \nu) $ using $189 \mathrm{fb}^{-1}$ of data at Belle II

Junkerkalefeld¹

2022

Proceedings of 41st International Conference on High Energy Physics — PoS(ICHEP2022)

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In this work a measurement of the ratio of branching fractions of inclusive semileptonic 𝐵 meson decays, 𝑅(𝑋 𝑒/𝜇 ) = B (𝐵 → 𝑋𝑒𝜈)/B (𝐵 → 𝑋 𝜇𝜈) is reported as a probe of 𝑒 − 𝜇 universality. Electron-positron collisions collected at the Υ(4𝑆) resonance with the Belle II detector corresponding to 189 fb −1 of integrated luminosity are used. One 𝐵 meson is reconstructed in its fully hadronical decays, while the semileptonic 𝐵 meson decay is selected by demanding the reconstructed lepton to have a momentum in the 𝐵 rest frame above 1.3 GeV/𝑐. We find 𝑅(𝑋 𝑒/𝜇 ) = 1.033 ± 0.010 ± 0.019. The first contribution to the uncertainty is statistical, the second systematic. This is the most precise branching-fraction based test of 𝑒 − 𝜇 universality in semileptonic 𝐵 decays to date and agrees with the Standard Model expectation within 1.3 𝜎.

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Section: Henrik Junkerkalefeldsupporting

confidence: 92%

A measurement of the ratio of light-lepton inclusive semileptonic $B$ decay rates $R(X_{e/\mu})$ = $\mathcal{B}(B \rightarrow X e \nu)$ / $\mathcal{B}(B \rightarrow X \mu \nu) $ using $189 \mathrm{fb}^{-1}$ of data at Belle II

Junkerkalefeld¹

2022

Proceedings of 41st International Conference on High Energy Physics — PoS(ICHEP2022)

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“…in refs. [118,119]. In this respect, it is worth emphasising that contrary to the naive expectation, the coefficient of the Darwin operator is found to be sizeable; more precisely, it results to be one order of magnitude larger than the corresponding ones at dimension-five.…”

Section: Jhep01(2023)004mentioning

confidence: 70%

Disintegration of beauty: a precision study

Lenz

Laura

Rusov

2023

J. High Energ. Phys.

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We update the Standard Model (SM) predictions for B-meson lifetimes within the heavy quark expansion (HQE). Including for the first time the contribution of the Darwin operator, SU(3)F breaking corrections to the matrix element of dimension-six four-quark operators and the so-called eye-contractions, we obtain for the total widths $$ \Gamma \left({B}^{+}\right)=\left({0.58}_{-0.07}^{+0.11}\right){\textrm{ps}}^{-1},\Gamma \left({B}_d\right)=\left({0.63}_{-0.07}^{+0.11}\right){\textrm{ps}}^{-1},\Gamma \left({B}_s\right)=\left({0.63}_{-0.07}^{+0.11}\right){\textrm{ps}}^{-1} $$ Γ B + = 0.58 − 0.07 + 0.11 ps − 1 , Γ B d = 0.63 − 0.07 + 0.11 ps − 1 , Γ B s = 0.63 − 0.07 + 0.11 ps − 1 , and for the lifetime ratios τ(B+)/τ(Bd) = 1.086 ± 0.022, τ(Bs)/τ(Bd) = 1.003 ± 0.006 (1.028 ± 0.011). The two values for the last observable arise from using two different sets of input for the non-perturbative parameters $$ {\mu}_{\pi}^2\left({B}_d\right),{\mu}_G^2\left({B}_d\right) $$ μ π 2 B d , μ G 2 B d , and $$ {\rho}_D^3\left({B}_d\right) $$ ρ D 3 B d as well as from different estimates of the SU(3)F breaking in these parameters. Our results are overall in very good agreement with the corresponding experimental data, however, there seems to emerge a tension in τ(Bs)/τ(Bd) when considering the second set of input parameters. Specifically, this observable is extremely sensitive to the size of the parameter $$ {\rho}_D^3\left({B}_d\right) $$ ρ D 3 B d and of the SU(3)F breaking effects in $$ {\mu}_{\pi}^2,{\mu}_G^2 $$ μ π 2 , μ G 2 and $$ {\rho}_D^3 $$ ρ D 3 ; hence, it is of utmost importance to be able to better constrain all these parameters. In this respect, an extraction of $$ {\mu}_{\pi}^2\left({B}_s\right),{\mu}_G^2\left({B}_s\right),{\rho}_D^3\left({B}_s\right) $$ μ π 2 B s , μ G 2 B s , ρ D 3 B s from future experimental data on inclusive semileptonic Bs-meson decays or from direct non-perturbative calculations, as well as more insights about the value of $$ {\rho}_D^3(B) $$ ρ D 3 B extracted from fits to inclusive semileptonic B-decays, would be very helpful in reducing the corresponding theory uncertainties.

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“…These inputs and the predictions for the semitauonic branching ratios are shown in Table I. (For the inclusive prediction, using the different evaluations R(X c ) = 0.221 ± 0.004 [22] and/or B(B → X c ν ) = (10.48 ± 0.13)% [23], result in slightly different predictions: B(B → X c τ ν) = (2.34 ± 0.06)% [11,23], 14). The gray error bar and the shaded band shows the allowed range derived in Eq.…”

Section: Numerical Results and Implicationsmentioning

confidence: 99%

Exploring the $τ$ polarization in $B\to Xτ\barν$ along different axes

Bernlochner¹,

Ligeti²,

Papucci³

et al. 2023

Preprint

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The τ polarization in semileptonic B decays provides probes of new physics complementary to decay rate distributions of the three-body final state. Prior calculations for inclusive decays used a definition for the polarization axis that is different from the choice used in calculations (and the only measurement) for exclusive channels. To compare inclusive and exclusive predictions, we calculate the τ polarization in inclusive B → Xτ ν using the same choice as in the exclusive decays, and construct a sum rule relating the inclusive τ polarization to a weighted sum of exclusive decay polarizations. We use this relation, experimental data, and theoretical predictions for the decays to the lightest charm or up-type hadrons to make predictions for excited channels.

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Standard Model predictions for lepton flavour universality ratios of inclusive semileptonic B decays

Cited by 16 publications

References 43 publications

A measurement of the ratio of light-lepton inclusive semileptonic \(B\) decay rates \(R(X_{e/\mu})\) = \(\mathcal{B}(B \rightarrow X e \nu)\) / \(\mathcal{B}(B \rightarrow X \mu \nu) \) using \(189 \mathrm{fb}^{-1}\) of data at Belle II

A measurement of the ratio of light-lepton inclusive semileptonic \(B\) decay rates \(R(X_{e/\mu})\) = \(\mathcal{B}(B \rightarrow X e \nu)\) / \(\mathcal{B}(B \rightarrow X \mu \nu) \) using \(189 \mathrm{fb}^{-1}\) of data at Belle II

Disintegration of beauty: a precision study

Exploring the $τ$ polarization in $B\to Xτ\barν$ along different axes

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