Hint of a new scalar interaction in LHCb data?

Abstract

We explain recent LHCb measurements of the lepton universality ratios, $R_{D^{(\ast )}}^{\tau /\ell }\equiv \frac{\mathcal{B}(\bar{B}\to D^{(\ast )+}{\tau }^{-}{\bar{\nu }}_{\tau })}{\mathcal{B}(\bar{B}\to D^{(\ast )+}{\ell }^{-}{\bar{\nu }}_{\ell })}$ and ${R({\Lambda }_c^{+})}^{\tau /\ell }\equiv \frac{\mathcal{B}({\Lambda }_b\to {\Lambda }_c^{+}{\tau }^{-}{\bar{\nu }}_{\tau })}{\mathcal{B}({\Lambda }_b\to {\Lambda }_c^{+}{\ell }^{-}{\bar{\nu }}_{\ell })}$ with $\ell =\mu$, via new physics that affects $R_D^{\tau /\ell }$ and $R({\Lambda }_c^{+}{)}^{\tau /\ell }$ but not $R_{D^{\ast }}^{\tau /\ell }$. The scalar operator in the effective theory for new physics is indicated. We find that the forward-backward asymmetry and $\tau$ polarization in $\bar{B}\to D^{+}{\tau }^{-}{\bar{\nu }}_{\tau }$ and ${\Lambda }_b\to {\Lambda }_c^{+}{\tau }^{-}{\bar{\nu }}_{\tau }$ decays are significantly affected by the scalar interaction. We construct a simple two Higgs doublet model as a realization of our scenario and consider lepton universality in semileptonic charm and top decays, radiative $B$ decay, $B$-mixing, and $Z\to b\bar{b}$.

7 pages, 2 figures, 3 tables

References in corpus (9)

• 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
• Confronting lepton flavor universality violation in B decays with high-$p_T$ tau lepton searches at LHC
• Implications of lepton flavor universality violations in B decays
• The lifetime of the $B_c^{-}$ meson and the anomalies in $B\to D^{(\ast )}\tau \nu$
• Measurement of the $\tau$ lepton polarization and $R(D^{\ast })$ in the decay $\bar{B}\to D^{\ast }{\tau }^{-}{\bar{\nu }}_{\tau }$ with one-prong hadronic $\tau$ decays at Belle
• Observation of the decay ${\Lambda }_b^0\to {\Lambda }_c^{+}{\tau }^{-}{\overline{\nu }}_{\tau }$
• Precise predictions for ${\Lambda }_b\to {\Lambda }_c$ semileptonic decays
• Single charged Higgs boson production at the LHC
• Interpreting LHCb's ${\Lambda }_b\to {\Lambda }_c\tau \bar{\nu }$ measurement and puzzles in semileptonic ${\Lambda }_b$ decays