$b\to c\tau {\bar{\nu }}_{e,\mu }$ contributions to $R(D^{(\ast )})$

Abstract

The $R(D^{(\ast )})$ puzzle stands for a $\sim 3\sigma$ violation of lepton flavor universality between the decay rates of $B\to D^{(\ast )}\tau \nu$ and $B\to D^{(\ast )}\ell \nu$, where $\ell =e,\mu$. If it is accounted for by new physics, there is no reason in general that the relevant neutrinos are, respectively, ${\nu }_{\tau }$ and ${\nu }_{\ell }$. We study whether the $\tau$ related rate could be enhanced by significant contributions to $B\to D^{(\ast )}\tau {\nu }_{\ell }$ from a class of operators in the Standard Model Effective Field Theory (SMEFT). We find the upper bounds from forbidden or rare meson decays imply that the contributions from the lepton flavor violating processes account for no more than about $4\%$ of the required shift. Yet, no fine-tuned flavor alignment is required for the new physics. Searching for the related high-$p_T$ process $pp\to {\tau }^{\pm }{\mu }^{\mp }$ can at present put a lower bound on the scale of the lepton flavor violating new physics that is a factor of $2.2$ weaker than the bound from meson decays. An exception to our conclusion arises from a specific combination of scalar and tensor SMEFT operators.

arXiv comment10 pages; v2: References added; v3: Added discussion of scalar and tensor operators and of flavor constraints from charmed mesons

References in corpus (26)

• Confronting lepton flavor universality violation in B decays with high-$p_T$ tau lepton searches at LHC
• The lifetime of the $B_c^{-}$ meson and the anomalies in $B\to D^{(\ast )}\tau \nu$
• Revisiting $B\to D\ell \nu$
• $R(D^{\ast })$, $|V_{cb}|$, and the Heavy Quark Symmetry relations between form factors
• High-$p_T$ dilepton tails and flavour physics
• Scalar leptoquarks from GUT to accommodate the $B$-physics anomalies
• Revisiting Lepton Flavour Universality in B Decays
• Scalar contributions to $b\to c(u)\tau \nu$ transitions
• Extraction of $|V_{cb}|$ from $B\to D^{(\ast )}\ell {\nu }_{\ell }$ and the Standard Model predictions of $R(D^{(\ast )})$
• What is the scale of new physics behind the $B$-flavour anomalies?
• Revisiting the one leptoquark solution to the $R(D^{(\ast )})$ anomalies and its phenomenological implications
• The Mono-Tau Menace: From $B$ Decays to High-$p_T$ Tails
• Measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^{\ast })$ with a semileptonic tagging method
• Implications of scalar and tensor explanations of $R_{D^{(\ast )}}$
• Lepton Flavor Violation and Dilepton Tails at the LHC
• Interplay of dineutrino modes with semileptonic rare $\mathbf{B}$-decays
• Lepton flavor violating decays of vector quarkonia and of the $Z$ boson
• Lepton flavor violating quarkonium decays
• Bottom-Flavored Mono-Tau Tails at the LHC
• ${\rm Y}$ and $\psi$ leptonic decays as probes of solutions to the $R_D^{(\ast )}$ puzzle
• Non-resonant new physics search at the LHC for the $b\to c\tau \nu$ anomalies
• Establishing a Search for $b\to s{\ell }^{+}{\ell }^{-}$ Anomalies at the LHC
• Revisiting mono-$\tau$ tails at the LHC
• Lepton universality and lepton flavor conservation tests with dineutrino modes
• Search for opposite sign muon-tau pair and a b-jet at LHC in the context of flavor anomalies
• Flavor violation at LHC in events with two opposite sign leptons and a $b$-jet

Cited by in corpus (2)

• Drell-Yan Tails Beyond the Standard Model
• On the EFT validity for Drell-Yan tails at the LHC