A Light shed on Lepton Flavor Universality in B decays

Abstract

At the back of succeeding measurements of anomalies in semileptonic decays at LHCb and several collider experiments hinting at the possible violation of lepton flavor universality, we undertake a concise review of theoretical foundations of the tree- and loop-level $b$-hadron decays, $b\to cl{\nu }_l$ and $b\to s{l}^{+}{l}^{-}$ along with experimental environments. We revisit the world averages for $R_{D(D^{\ast })}$, $R_{K(K^{\ast })}$, $R_{J/\psi }$, and $R_{{\eta }_c}$, for the semileptonic transitions and provide results within the framework of the relativistic independent quark model in addition to the results from model-independent studies. If the ongoing evaluation of the data of LHC Run 2 confirms the measurements of Run 1, then the statistical significance of the effect in each decay channel is likely to reach 5~$\sigma$. A confirmation of these measurements would soon turn out to be the first remarkable observation of physics beyond the Standard Model providing a wider outlook on the understanding of New Physics.

arXiv commentUpdated, revised, and journal version. This article belongs to the Special Issue Search for New Physics at the LHC and Future Colliders

References in corpus (69)

• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of summer 2016
• Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm
• LHCb Detector Performance
• Test of lepton universality with $B^0\to K^{\ast 0}{\ell }^{+}{\ell }^{-}$ decays
• Angular analysis of the $B^0\to K^{\ast 0}{\mu }^{+}{\mu }^{-}$ decay using $3\,\mbox{fb}^{-1}$ of integrated luminosity
• One Leptoquark to Rule Them All: A Minimal Explanation for $R_{D^{(\ast )}}$, $R_K$ and $(g-2{)}_{\mu }$
• Measurement of the $\tau$ lepton polarization and $R(D^{\ast })$ in the decay $\bar{B}\to D^{\ast }{\tau }^{-}{\bar{\nu }}_{\tau }$
• On the Standard Model predictions for $R_K$ and $R_{K^{\ast }}$
• Explaining $h\to {\mu }^{\pm }{\tau }^{\mp }$, $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ and $B\to K{\mu }^{+}{\mu }^{-}/B\to K{e}^{+}{e}^{-}$ in a two-Higgs-doublet model with gauged $L_{\mu }-L_{\tau }$
• Measurement of the Differential Branching Fraction and Forward-Backword Asymmetry for B->K(*)l+l-
• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of 2018
• Search for lepton-universality violation in $B^{+}\to K^{+}{\ell }^{+}{\ell }^{-}$ decays
• Dressing L_mu - L_tau in Color
• Model independent constraints on leptoquarks from rare processes
• Differential branching fractions and isospin asymmetries of $B\to K^{(\ast )}{\mu }^{+}{\mu }^{-}$ decays
• Effective field theory approach to $b\to s\ell {\ell }^{(\prime )}$, $B\to K^{(\ast )}\nu \bar{\nu }$ and $B\to D^{(\ast )}\tau \nu$ with third generation couplings
• Simultaneous Explanation of $R(D^{(\ast )})$ and $b\to s{\mu }^{+}{\mu }^{-}$: The Last Scalar Leptoquarks Standing
• Vector leptoquark resolution of $R_K$ and $R_{D^{(\ast )}}$ puzzles
• Testing leptoquark models in $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$
• Measurement of the ratio of the $B^0\to D^{\ast -}{\tau }^{+}{\nu }_{\tau }$ and $B^0\to D^{\ast -}{\mu }^{+}{\nu }_{\mu }$ branching fractions using three-prong $\tau$-lepton decays
• Angular analysis and differential branching fraction of the decay $B_s^0\to \varphi {\mu }^{+}{\mu }^{-}$
• $R_K$ and future $b\to s\ell \ell$ BSM opportunities
• Simultaneous Explanation of the $R_K$ and $R(D^{(\ast )})$ Puzzles
• $B$ Meson Anomalies in a Pati-Salam Model within the Randall-Sundrum Background
• Measurement of the ratio of branching fractions $\mathcal{B}(B_c^{+}\to J/\psi {\tau }^{+}{\nu }_{\tau })$/$\mathcal{B}(B_c^{+}\to J/\psi {\mu }^{+}{\nu }_{\mu })$
• A model of vector leptoquarks in view of the $B$-physics anomalies
• Exclusive semileptonic and nonleptonic decays of the Bc meson
• Importance of Loop Effects in Explaining the Accumulated Evidence for New Physics in B Decays with a Vector Leptoquark
• Review of Lepton Universality tests in B decays
• B-decay Anomalies in a Composite Leptoquark Model
• Weak decays of the B_c meson to charmonium and D mesons in the relativistic quark model
• Family non-universal Z' models with protected flavor-changing interactions
• Lepton Flavor Non-Universality in B-meson Decays from a U(2) Flavor Model
• Simultaneous Explanation of the $R_K$ and $R_{D^{(\ast )}}$ Puzzles: a Model Analysis
• Measurement of angular parameters from the decay ${\mathrm{B}}^0\to {\mathrm{K}}^{\ast 0}{\mu }^{+}{\mu }^{-}$ in proton-proton collisions at $\sqrt{s}=$ 8 TeV
• Study of exclusive semileptonic and nonleptonic decays of $B_c^{-}$ in a nonrelativistic quark model
• Branching fraction measurements of the rare $B_s^0\to \varphi {\mu }^{+}{\mu }^{-}$ and $B_s^0\to f_2^{\prime }(1525){\mu }^{+}{\mu }^{-}$ decays
• B-meson decay constants: a more complete picture from full lattice QCD
• New Physics effect on $B_c\to J/\psi \tau \bar{\nu }$ in relation to the $R_{D^{(\ast )}}$ anomaly
• Test of lepton flavor universality and search for lepton flavor violation in $B\to K\ell \ell$ decays
• Combined Explanations of the $b\to s{\mu }^{+}{\mu }^{-}$ and $b\to c{\tau }^{-}\bar{\nu }$ Anomalies: a General Model Analysis
• Semileptonic decays $B_c\to ({\eta }_c,J/\Psi )l\nu$ in the perturbative QCD approach
• Semileptonic and non-leptonic B_c decays
• Addressing the B-physics anomalies in a fundamental Composite Higgs Model
• Theory determination of $\bar{B}\to D^{(\ast )}{\ell }^{-}\bar{\nu }$ form factors at $\mathcal{O}(1/m_c^2)$
• Observation of two excited B${}_{\mathrm{c}}^{+}$ states and measurement of the B${}_{\mathrm{c}}^{+}$(2S) mass in pp collisions at $\sqrt{s}=$ 13 TeV
• Improved measurement of the $π\rightarrow \mbox{e} ν$ branching ratio
• QED Corrections in $\bar{B}\to \bar{K}{\ell }^{+}{\ell }^{-}$ at the Double-Differential Level
• Tests of lepton universality using $B^0\to K_S^0{\ell }^{+}{\ell }^{-}$ and $B^{+}\to K^{\ast +}{\ell }^{+}{\ell }^{-}$ decays
• Bayesian fit analysis to full distribution data of $\bar{B}\to D^{(\ast )}\ell \bar{\nu }$: $|V_{cb}|$ determination and New Physics constraints
• Semitauonic $b$-hadron decays: A lepton flavor universality laboratory
• Challenges in Semileptonic B Decays
• Study of Bc --> J/psi pi, etac pi decays with perturbative QCD approach
• The role of right-handed neutrinos in $b\to c\tau \bar{\nu }$ anomalies
• Semileptonic and nonleptonic decays of B_c mesons to orbitally excited heavy mesons in the relativistic quark model
• Unified explanation of flavor anomalies, radiative neutrino mass and ANITA anomalous events in a vector leptoquark model
• Standard Model Predictions for Rare K and B Decays without New Physics Infection
• Correlating the anomalous results in $b\to s$ decays with inert Higgs doublet dark matter and muon $(g-2)$
• Weak productions of new charmonium in semi-leptonic decays of B_c
• QED in $\bar{B}\to \bar{K}{\ell }^{+}{\ell }^{-}$ LFU ratios: Theory versus Experiment, a Monte Carlo Study
• Semileptonic decays of $B_c$ mesons into charmonium states
• A global analysis of $b\to s\ell \ell$ data in heavy and light $Z^{\prime }$ models
• The cost of an ALP solution to the neutral $B$-anomalies
• Magnetic Dipole Transitions of $B_c$ and $B_c^{\ast }$ mesons in the Relativistic Independent Quark Model
• Lepton mass effects in exclusive semileptonic $B_c$-meson decays
• Flavour-changing neutral scalar interactions of the top quark
• The weak $B$, $B_s$ and $B_c$ decays to radially excited states
• Electromagnetic transitions of $(b\bar{c})$ bound system
• On the impact of meson mixing on $B_s\to \varphi ee$ angular observables at low $q^2$

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• Assessing Lepton Flavor Universality Violations in Semileptonic Decays
• Study of angular observables in exclusive semileptonic $B_c$ decays
• Search for nonresonant new physics signals in high-mass dilepton events produced in association with b-tagged jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV