Effective Theory Approach to New Physics with Flavour: General Framework and a Leptoquark Example

Abstract

Extending the Standard Model with higher-dimensional operators in an effective-field-theory (EFT) approach provides a systematic framework to study new-physics (NP) effects from a bottom-up perspective, as long as the NP scale is sufficiently large compared to the energies probed in the experimental observables. However, when taking into account the different quark and lepton flavours, the number of free parameters increases dramatically, which makes generic studies of the NP flavour structure infeasible. In this paper, we address this issue in view of the recently observed "flavour anomalies" in $B$-meson decays, which we take as a motivation to develop a general framework that allows us to systematically reduce the number of flavour parameters in the EFT. This framework can be easily used in global fits to flavour observables at Belle II and LHCb as well as in analyses of flavour-dependent collider signatures at the LHC. Our formalism represents an extension of the well-known minimal-flavour-violation approach, and uses Froggatt-Nielsen charges to define the flavour power-counting. As a relevant illustration of the formalism, we apply it to the flavour structures which could be induced by a $U_1$ vector leptoquark, which represents one of the possible explanations for the recent hints of flavour non-universality in semileptonic $B$-decays. We study the phenomenological viability of this specific framework performing a fit to low-energy flavour observables.

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References in corpus (53)

• Dimension-Six Terms in the Standard Model Lagrangian
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• Minimal Flavour Violation: an effective field theory approach
• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of summer 2016
• Measurement of an Excess of B -> D(*) Tau Nu Decays and Implications for Charged Higgs Bosons
• B-physics anomalies: a guide to combined explanations
• Search for lepton-universality violation in $B^{+}\to K^{+}{\ell }^{+}{\ell }^{-}$ decays
• A three-site gauge model for flavor hierarchies and flavor anomalies
• U(2) and Minimal Flavour Violation in Supersymmetry
• Implications of LHCb measurements and future prospects
• $B$ Meson Anomalies in a Pati-Salam Model within the Randall-Sundrum Background
• Combined analysis of semileptonic $B$ decays to $D$ and $D^{\ast }$: $R(D^{(\ast )})$, $|V_{cb}|$, and new physics
• Gauge leptoquark as the origin of B-physics anomalies
• The $B\to D\ell \nu$ form factors at nonzero recoil and $|V_{cb}|$ from $2+1$-flavor lattice QCD
• $B\to Dl\nu$ Form Factors at Non-Zero Recoil and Extraction of $|V_{cb}|$
• Closing the window on single leptoquark solutions to the $B$-physics anomalies
• A model of vector leptoquarks in view of the $B$-physics anomalies
• B-decay discrepancies after Moriond 2019
• Revisiting $B\to D\ell \nu$
• Baryon Number and Lepton Universality Violation in Leptoquark and Diquark Models
• $SU(2)\times U(1)$ gauge invariance and the shape of new physics in rare $B$ decays
• Measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^{\ast })$ with a semileptonic tagging method
• $R(D^{\ast })$, $|V_{cb}|$, and the Heavy Quark Symmetry relations between form factors
• Importance of Loop Effects in Explaining the Accumulated Evidence for New Physics in B Decays with a Vector Leptoquark
• Emerging patterns of New Physics with and without Lepton Flavour Universal contributions
• Extraction of $|V_{cb}|$ from $B\to D^{(\ast )}\ell {\nu }_{\ell }$ and the Standard Model predictions of $R(D^{(\ast )})$
• The Rare Decays $K^{+}\to {\pi }^{+}\nu \bar{\nu }$\ and $K_L\to {\mu }^{+}{\mu }^{-}$\ Beyond Leading Logarithms
• Leptoquark Flavor Patterns & B Decay Anomalies
• Maximal Flavour Violation: a Cabibbo mechanism for leptoquarks
• New Physics in $b\to s{\ell }^{+}{\ell }^{-}$ confronts new data on Lepton Universality
• The Mono-Tau Menace: From $B$ Decays to High-$p_T$ Tails
• Global fit to $b\to c\tau \nu$ transitions
• New Limit on Muon and Electron Lepton Number Violation from $K_L^0\to {\mu }^{\pm }{e}^{\mp }$ Decay
• Revisiting the vector leptoquark explanation of the B-physics anomalies
• Continuing search for new physics in $b\to s\mu \mu$ decays: two operators at a time
• Left-Right SU(4) Vector Leptoquark Model for Flavor Anomalies
• Pati-Salam explanations of the B-meson anomalies
• Low-energy signatures of the ${\mathrm{PS}}^3$ model: from $B$-physics anomalies to LFV
• High-pT Signatures in Vector-Leptoquark Models
• On the Importance of Electroweak Corrections for B Anomalies
• Constraining new physics in $b\to c\ell \nu$ transitions
• With or without U(2)? Probing non-standard flavor and helicity structures in semileptonic B decays
• B-decay anomalies in Pati-Salam SU(4)
• The Leptoquark Hunter's Guide: Large Coupling
• Search for the decays $B_s^0\to {\tau }^{+}{\tau }^{-}$ and $B^0\to {\tau }^{+}{\tau }^{-}$
• Revisiting the new-physics interpretation of the $b\to c\tau \nu$ data
• Anomaly free Froggatt-Nielsen models of flavor
• Minimal Flavour Violation and Beyond
• Signatures of a nonstandard Higgs from flavor physics
• A unified leptoquark model confronted with lepton non-universality in $B$-meson decays
• Probing Lepton Flavour Universality with $K\to \pi \nu \bar{\nu }$ decays
• Simplified Models of Flavourful Leptoquarks
• A vector leptoquark for the B-physics anomalies from a composite GUT

Cited by in corpus (38)

• SMEFTsim 3.0 -- a practical guide
• The Standard Model effective field theory at work
• Implications of new evidence for lepton-universality violation in $b\to s{\ell }^{+}{\ell }^{-}$ decays
• Flavour symmetries in the SMEFT
• Flavor Constraints from Unitarity and Analyticity
• Combined Constraints on First Generation Leptoquarks
• Scalar Leptoquarks in Leptonic Processes
• Interplay of dineutrino modes with semileptonic rare $\mathbf{B}$-decays
• Unified explanation of flavor anomalies, radiative neutrino mass and ANITA anomalous events in a vector leptoquark model
• Combined Explanation of the $Z\to b\bar{b}$ Forward-Backward Asymmetry, the Cabibbo Angle Anomaly, $\tau \to \mu \nu \nu$ and $b\to s{\ell }^{+}{\ell }^{-}$ Data
• Combined explanation of $W$-mass, muon $g-2$, $R_{K^{(\ast )}}$ and $R_{D^{(\ast )}}$ anomalies in a singlet-triplet scalar leptoquark model
• Precise limits on the charge-$2/3$ $U_1$ vector leptoquark
• Leptoquarks in Oblique Corrections and Higgs Signal Strength: Status and Prospects
• Complete Lagrangian and Set of Feynman Rules for Scalar Leptoquarks
• Resonant third-generation leptoquark signatures at the Large Hadron Collider
• Resolving the Flavor Structure in the MFV-SMEFT
• What is Leading Order for LFV in SMEFT?
• Adding Flavor to the SMEFT
• Constraining flavour patterns of scalar leptoquarks in the effective field theory
• A model for the Singlet-Triplet Leptoquarks
• $B$ anomalies under the lens of electroweak precision
• Towards excluding a light $Z^{\prime }$ explanation of $b\to s{\ell }^{+}{\ell }^{-}$
• Fingerprinting CP-violating New Physics with $B\to K{\mu }^{+}{\mu }^{-}$
• Search for the lepton-flavour violating decays $B^0\to K^{\ast 0}{\tau }^{\pm }{\mu }^{\mp }$
• Opportunistic CP Violation
• Addendum to: Combined Constraints on First Generation Leptoquarks
• Drell-Yan production in third-generation gauge vector leptoquark models at NLO+PS in QCD
• Next-to-Leading-Order QCD Matching for $\Delta F=2$ Processes in Scalar Leptoquark Models
• Lepton flavour violation in rare ${\Lambda }_b$ decays
• Exploring the flavor structure of quarks and leptons with reinforcement learning
• Discrete symmetries and Efficient Counting of Operators
• New Perspectives for Testing Electron-Muon Universality
• Froggatt-Nielsen Meets the SMEFT
• Lepton Flavor Violation: From Muon Decays to Muon Colliders
• Testing the Froggatt-Nielsen Mechanism with Lepton Flavor and Number Violating Processes
• A composite Froggatt-Nielsen model of flavor
• Rare decay $t\to c\gamma \gamma$ via scalar leptoquark doublets
• Explaining the hints for lepton flavour universality violation with three $S_2$ leptoquark generations