Lepton-flavour non-universality of $\bar{B}\to D^{\ast }\ell \bar{\nu }$ angular distributions in and beyond the Standard Model

Abstract

We analyze in detail the angular distributions in $\bar{B}\to D^{\ast }\ell \bar{\nu }$ decays, with a focus on lepton-flavour non-universality. We investigate the minimal number of angular observables that fully describes current and upcoming datasets, and explore their sensitivity to physics beyond the Standard Model (BSM) in the most general weak effective theory. We apply our findings to the current datasets, extract the non-redundant set of angular observables from the data, and compare to precise SM predictions that include lepton-flavour universality violating mass effects. Our analysis shows that the current presentation of the experimental data is not ideal and prohibits the extraction of the full set of relevant BSM parameters, since the number of independent angular observables that can be inferred from data is limited to only four. We uncover a $\sim 4\sigma$ tension between data and predictions that is hidden in the redundant presentation of the Belle 2018 data on $\bar{B}\to D^{\ast }\ell \bar{\nu }$ decays. This tension specifically involves observables that probe $e-\mu$ lepton-flavour universality. However, we find inconsistencies in these data, which renders results based on it suspicious. Nevertheless, we discuss which generic BSM scenarios could explain the tension, in the case that the inconsistencies do not affect the data materially. Our findings highlight that $e-\mu$ non-universality in the SM, introduced by the finite muon mass, is already significant in a subset of angular observables with respect to the experimental precision.

18 pages, 2 figures, 3 tables

References in corpus (9)

• On the B to D* tau nu Sensitivity to New Physics
• New physics in the weak interaction of $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$
• $R(D^{\ast })$, $|V_{cb}|$, and the Heavy Quark Symmetry relations between form factors
• The $V_{cb}$ puzzle: an update
• Analyzing new physics in the decays ${\bar{B}}^0\to D^{(\ast )}{\tau }^{-}{\bar{\nu }}_{\tau }$ with form factors obtained from the covariant quark model
• The Azimuthal $B\to D^{\ast }{\tau }^{-}\overline{{\nu }_{\tau }}$ Angular Distribution with Tensor Operators
• Measurement of the form factors of the decay B0 -> D*- ell+ nu and determination of the CKM matrix element |Vcb|
• Tensions and correlations in $|V_{cb}|$ determinations
• Precise determination of the CKM matrix element $\left|V_{cb}\right|$ with ${\bar{B}}^0\to D^{\ast +}{\ell }^{-}{\bar{\nu }}_{\ell }$ decays with hadronic tagging at Belle

Cited by in corpus (26)

• 50 Years of Quantum Chromodynamics
• Semileptonic form factors for $B\to D^{\ast }\ell \nu$ at nonzero recoil from 2 + 1-flavor lattice QCD
• EOS -- A Software for Flavor Physics Phenomenology
• Unveiling Hidden Physics at the LHC
• Impact of ${\Lambda }_b\to {\Lambda }_c\tau \nu$ measurement on New Physics in $b\to cl\nu$ transitions
• Mounting Evidence for the Violation of Lepton Flavor Universality
• Towards testing the magnetic moment of the tau at one part per million
• Measurement of Differential Distributions of $B\to D^{\ast }\ell {\bar{\nu }}_{\ell }$ and Implications on $|V_{cb}|$
• Constrained second-order power corrections in HQET: $R(D^{(\ast )})$, $|V_{cb}|$, and new physics
• The Forward-Backward Asymmetry in $B\to D^{\ast }\ell \nu$: One more hint for Scalar Leptoquarks?
• Determination of $|V_{cb}|$ using ${\overline{B}}^0\to D^{\ast +}{\ell }^{-}{\bar{\nu }}_{\ell }$ decays with Belle II
• Computing Tools for Effective Field Theories
• Toward a complete description of $b\to u{\ell }^{-}\bar{\nu }$ decays within the Weak Effective Theory
• $\bar{B}\to D^{(\ast )}\ell \bar{X}$ decays in effective field theory with massive right-handed neutrinos
• Next-to-Leading-Order QCD Matching for $\Delta F=2$ Processes in Scalar Leptoquark Models
• Implications for the $\Delta A_{FB}$ anomaly in ${\bar{B}}^0\to D^{\ast +}{\ell }^{-}\bar{\nu }$ using a new Monte Carlo Event Generator
• The forward-backward asymmetry and differences of partial moments in inclusive semileptonic B decays
• New physics contributions to moments of inclusive $b\to c$ semileptonic decays
• Tests of light-lepton universality in angular asymmetries of $B^0\to D^{\ast -}\ell \nu$ decays
• Singlet vector leptoquark model facing recent LHCb and BABAR measurements
• Flavour anomalies meet flavour symmetry
• Explaining the hints for lepton flavour universality violation with three $S_2$ leptoquark generations
• Standard Model predictions for Lepton Flavour Universality ratios of inclusive semileptonic $B$ decays
• EOS -- A Software for Flavor Physics Phenomenology
• Lepton universality tests and searches for new physics in charged current decays at Belle II
• Joint LHCb--Belle II Prospects to Constrain New Physics in $B\to D^{(\ast )}\tau \nu$