${\rm Y}$ and $\psi$ leptonic decays as probes of solutions to the $R_D^{(\ast )}$ puzzle

Abstract

Experimental measurements of the ratios $R(D^{(\ast )})\equiv \frac{\Gamma (B\to D^{(\ast )}\tau \nu )}{\Gamma (B\to D^{(\ast )}\ell \nu )}$ ($\ell =e,\mu$) show a $3.9\sigma$ deviation from the Standard Model prediction. In the absence of light right-handed neutrinos, a new physics contribution to $b\to c\tau \nu$ decays necessarily modifies also $b\bar{b}\to {\tau }^{+}{\tau }^{-}$ and/or $c\bar{c}\to {\tau }^{+}{\tau }^{-}$ transitions. These contributions lead to violation of lepton flavor universality in, respectively, ${\rm Y}$ and $\psi$ leptonic decays. We analyze the constraints resulting from measurements of the leptonic vector-meson decays on solutions to the $R(D^{(\ast )})$ puzzle. Available data from BaBar and Belle can already disfavor some of the new physics explanations of this anomaly. Further discrimination can be made by measuring ${\rm Y}(1S,2S,3S)\to \tau \tau$ in the upcoming Belle II experiment.

Version published in JHEP, 17 pages, 7 figures

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• New physics solutions for $R_D$ and $R_{D^{\ast }}$
• Flavourful $Z^{\prime }$ portal for vector-like neutrino Dark Matter and $R_{K^{(\ast )}}$
• Challenges in Semileptonic B Decays
• Unveiling Hidden Physics at the LHC
• Footprints of leptoquarks: from $R_{K^{(\ast )}}$ to $K\to \pi \nu \bar{\nu }$
• Global fit to $b\to c\tau \nu$ anomalies as of Spring 2024
• Coloured Scalar Mediated Nucleon Decays to Invisible Fermion
• CP Violation in ${\bar{B}}^0\to D^{\ast +}{\mu }^{-}{\bar{\nu }}_{\mu }$
• Simultaneous interpretation of $K$ and $B$ anomalies in terms of chiral-flavorful vectors
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• Precision measurement of the $\mathcal{B}({\rm Y}(3S)\to {\tau }^{+}{\tau }^{-})/\mathcal{B}({\rm Y}(3S)\to {\mu }^{+}{\mu }^{-})$ ratio
• Extra gauge bosons and lepton flavor universality violation in ${\rm Y}$ and $B$ meson decays
• Relations between $b\to c\tau \nu$ Decay Modes in Scalar Models
• Testing Lepton Flavour Universality in ${\rm Y}(4S)$ Decays
• $b\to c\tau {\bar{\nu }}_{e,\mu }$ contributions to $R(D^{(\ast )})$