Including resonant contributions from LHCb muon data enhances standard model predictions for B to K(*) tau tau decays and makes short-distance new physics comparable to or larger than resonant effects over the full q2 range.
Measurement of the branching ratio of $\bar{B}^0 \rightarrow D^{*+} \tau^- \bar{\nu}_{\tau}$ relative to $\bar{B}^0 \rightarrow D^{*+} \ell^- \bar{\nu}_{\ell}$ decays with a semileptonic tagging method
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abstract
We report a measurement of the ratio ${\cal R}(D^*) = {\cal B}(\bar{B}^0 \rightarrow D^{*+} \tau^- \bar{\nu}_{\tau})/{\cal B}(\bar{B}^0 \rightarrow D^{*+} \ell^- \bar{\nu}_{\ell})$, where $\ell$ denotes an electron or a muon. The results are based on a data sample containing $772\times10^6$ $B\bar{B}$ pairs recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. We select a sample of $B^0 \bar{B}^0$ pairs by reconstructing both $B$ mesons in semileptonic decays to $D^{*\mp} \ell^{\pm}$. We measure ${\cal R}(D^*)= 0.302 \pm 0.030({\rm stat)} \pm 0.011({\rm syst)}$, which is within $1.6 \sigma$ of the Standard Model theoretical expectation, where the standard deviation $\sigma$ includes systematic uncertainties. We use this measurement to constrain several scenarios of new physics in a model-independent approach.
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Partial compositeness in the minimal fundamental partial compositeness (MFPC) model explains B-meson flavour anomalies while also solving the SM naturalness problem.
Angular observables in B→D(*)ℓν decays can distinguish Lorentz structures of new physics contributions fitted to measured R(D(*)) ratios, even when those ratios agree with the Standard Model.
A tauphilic leptoquark model with S1 explaining R(D(*)), ~R2 fitting B to K nu nu via right-handed coefficients, and S3 satisfying Delta m_Bs via mixing predicts subdominant negative C_VL, dominant positive C_SL, C9^LQ approx +1, and masses below 3 TeV.
LHCb measures R(D*) and R(J/ψ); combined LHCb+Belle data yield 3.1σ tension with SM in R(D) and R(D*).
citing papers explorer
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Impact of Hadronic Resonances on $B\to K^{(*)}\tau^+\tau^-$ decays
Including resonant contributions from LHCb muon data enhances standard model predictions for B to K(*) tau tau decays and makes short-distance new physics comparable to or larger than resonant effects over the full q2 range.
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Flavour anomalies and (fundamental) partial compositeness
Partial compositeness in the minimal fundamental partial compositeness (MFPC) model explains B-meson flavour anomalies while also solving the SM naturalness problem.
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Lepton Flavor Universality tests through angular observables of $\overline{B}\to D^{(\ast)}\ell\overline{\nu}$ decay modes
Angular observables in B→D(*)ℓν decays can distinguish Lorentz structures of new physics contributions fitted to measured R(D(*)) ratios, even when those ratios agree with the Standard Model.
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$B$ anomalies and the tauphilic leptoquark model
A tauphilic leptoquark model with S1 explaining R(D(*)), ~R2 fitting B to K nu nu via right-handed coefficients, and S3 satisfying Delta m_Bs via mixing predicts subdominant negative C_VL, dominant positive C_SL, C9^LQ approx +1, and masses below 3 TeV.
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Lepton flavour universality in charged-current $B$ decays
LHCb measures R(D*) and R(J/ψ); combined LHCb+Belle data yield 3.1σ tension with SM in R(D) and R(D*).