Remarks on the Standard Model predictions for $R(D)$ and $R(D^{\ast })$

Abstract

Semileptonic $b\to c$ transitions, and in particular the ratios $R(D^{(\ast )})=\frac{\Gamma (B\to D^{(\ast )}\tau \nu )}{\Gamma (B\to D^{(\ast )}\ell \nu )}$, can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by BaBar, Belle and LHCb and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that $R(D)$ might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In constrast, the Standard Model prediction for $R(D^{\ast })$ is found to be more robust, since possible pollutions from $B^{\ast }$ contributions turn out to be negligibly small, which indicates that $R(D^{\ast })$ is a promising observable for searches of new physics.

11 pages, 3 figures; v2: minor corrections, matches published version

References in corpus (12)

• On the B to D* tau nu Sensitivity to New Physics
• Measurement of the branching ratio of ${\bar{B}}^0\to D^{\ast +}{\tau }^{-}{\bar{\nu }}_{\tau }$ relative to ${\bar{B}}^0\to D^{\ast +}{\ell }^{-}{\bar{\nu }}_{\ell }$ decays with a semileptonic tagging method
• Implications of lepton flavor universality violations in B decays
• New physics in the weak interaction of $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$
• Leptoquark model to explain the $B$-physics anomalies, $R_K$ and $R_D$
• Leptoquark Flavor Patterns & B Decay Anomalies
• Phenomenology of an $SU(2)\times SU(2)\times U(1)$ model with lepton-flavour non-universality
• New Physics in the Visible Final States of $B\to D^{(\ast )}\tau \nu$
• Measurement of the form factors of the decay B0 -> D*- ell+ nu and determination of the CKM matrix element |Vcb|
• Strong D* -> D+pi and B* -> B+pi couplings
• Precision lattice QCD computation of the $B^{\ast }B\pi$ coupling
• Study of semileptonic ${\bar{B}}^{\ast }\to P\ell {\bar{\nu }}_{\ell }$ decays

Cited by in corpus (2)

• Probing new physics in ${\bar{B}}^0\to D^{(\ast )}{\tau }^{-}{\bar{\nu }}_{\tau }$ using the longitudinal, transverse, and normal polarization components of the tau lepton
• $B_s\to D_s^{\ast }$ Form Factors for the full $q^2$ range from Lattice QCD