With or without U(2)? Probing non-standard flavor and helicity structures in semileptonic B decays

Abstract

Motivated by the recent hints of lepton flavor universality violation observed in semileptonic $B$ decays, we analyze how to test flavor and helicity structures of the corresponding amplitudes in view of future data. We show that the general assumption that such non-standard effects are controlled by a $U(2{)}_q\times U(2{)}_{\ell }$ flavor symmetry, minimally broken as in the Standard Model Yukawa sector, leads to stringent predictions on leptonic and semileptonic $B$ decays. Future measurements of $R_{D^{(\ast )}}$, $R_{K^{(\ast )}}$, $\mathcal{B}({\bar{B}}_{c,u}\to \ell \bar{\nu })$, $\mathcal{B}(\bar{B}\to \pi \ell \bar{\nu })$, $\mathcal{B}(B\to \pi \ell \bar{\ell })$, $\mathcal{B}(B_{s,d}\to \ell {\bar{\ell }}^{(\prime )})$, as well as various polarization asymmetries in $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$ decays, will allow to prove or falsify this general hypothesis independently of its dynamical origin.

12 pages, 4 figures (v2: very minor modifications)

References in corpus (14)

• Test of lepton universality using $B^{+}\to K^{+}{\ell }^{+}{\ell }^{-}$ decays
• Measurement of the Differential Branching Fraction and Forward-Backword Asymmetry for B->K(*)l+l-
• Search for lepton-universality violation in $B^{+}\to K^{+}{\ell }^{+}{\ell }^{-}$ decays
• Simultaneous Explanation of the $R_K$ and $R(D^{(\ast )})$ Puzzles
• Gauge leptoquark as the origin of B-physics anomalies
• The lifetime of the $B_c^{-}$ meson and the anomalies in $B\to D^{(\ast )}\tau \nu$
• New physics in the weak interaction of $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$
• 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
• Renormalization-group evolution of new physics contributions to (semi)leptonic meson decays
• New Physics effect on $B_c\to J/\psi \tau \bar{\nu }$ in relation to the $R_{D^{(\ast )}}$ anomaly
• Diagnosing lepton-nonuniversality in $b\to s\ell \ell$
• The role of the $S_3$ GUT leptoquark in flavor universality and collider searches
• Measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^{\ast })$ with a semileptonic tagging method
• Measurement of the $D^{\ast -}$ polarization in the decay $B^0\to D^{\ast -}{\tau }^{+}{\nu }_{\tau }$

Cited by in corpus (2)

• Lessons from the $B^{0,+}\to K^{\ast 0,+}{\mu }^{+}{\mu }^{-}$ angular analyses
• Effective Theory Approach to New Physics with Flavour: General Framework and a Leptoquark Example