The CKM unitarity problem: A trace of new physics at the TeV scale?

Abstract

After the recent high precision determinations of $V_{us}$ and $V_{ud}$, the first row of the CKM matrix shows more than $4\sigma$ deviation from unitarity. Two possible scenarios beyond the Standard Model can be investigated in order to fill the gap. If a 4th quark $b^{\prime }$ participates in the mixing, with $|V_{u{b}^{\prime }}|\sim 0.04$, then its mass should be no more than 6 TeV or so. A different solution can come from the introduction of the gauge horizontal family symmetry acting between the lepton families and spontaneously broken at the scale of about 6 TeV. Since the gauge bosons of this symmetry contribute to muon decay in positive interference with Standard Model, the Fermi constant is slightly smaller than the muon decay constant so that unitarity is recovered. Also the neutron lifetime problem, that is about $4\sigma$ discrepancy between the neutron lifetimes measured in beam and trap experiments, is discussed in the light of the these determinations of the CKM matrix elements.

arXiv comment11 pages, 10 figures

References in corpus (40)

• Minimal Flavour Violation: an effective field theory approach
• Precision Tau Physics
• Measurement of the neutron lifetime using a gravitational trap and a low-temperature Fomblin coating
• Reduced hadronic uncertainty in the determination of $V_{ud}$
• Improved Determination of the Neutron Lifetime
• Improved Calculation of Electroweak Radiative Corrections and the Value of V_ud
• Superallowed 0+ --> 0+ nuclear beta decays: 2014 critical survey, with precise results for Vud and CKM unitarity
• New physics searches in nuclear and neutron $\beta$ decay
• Mirror World and its Cosmological Consequences
• Radiative Corrections to Neutron and Nuclear Beta Decays Revisited
• Measurement of the Weak Axial-Vector Coupling Constant in the Decay of Free Neutrons Using a Pulsed Cold Neutron Beam
• Fermion Masses and Mixing Angles from SU(3) Family Symmetry and Unification
• Yukawa textures with an anomalous horizontal abelian symmetry
• Neutron -- Mirror Neutron Oscillation: How Fast Might It Be?
• Neutron - Mirror Neutron Oscillations: How Fast Might They Be?
• Measurement of the neutron lifetime using an asymmetric magneto- gravitational trap and in situ detection
• Determination of the Weak Axial Vector Coupling from a Measurement of the Beta-Asymmetry Parameter A in Neutron Beta Decay
• Neutron Lifetime and Axial Coupling Connection
• Light-meson leptonic decay rates in lattice QCD+QED
• Neutron lifetime measurements with the big gravitational trap for ultracold neutrons
• Neutron lifetime measurements using gravitationally trapped ultracold neutrons
• Abelian Flavour Symmetries in Supersymmetric Models
• Neutron lifetime puzzle and neutron -- mirror neutron oscillation
• New result for the neutron $\beta$-asymmetry parameter $A_0$ from UCNA
• More about neutron - mirror neutron oscillation
• Fast Neutron - Mirror Neutron Oscillation and Ultra High Energy Cosmic Rays
• Predictive Grand Unified Textures for Quark and Neutrino Masses and Mixings
• Unified picture of the particle and sparticle masses in SUSY GUT
• DAMA annual modulation effect and asymmetric mirror matter
• More missing VEV mechanism in supersymmetric SO(10) model
• Anomalous U(1) symmetry and missing doublet SU(5) model
• Flavor Violation in Theories with TeV Scale Quantum Gravity
• DAMA annual modulation and mirror Dark Matter
• $|V_{us}|$ from $K_{\ell 3}$ decay and four-flavor lattice QCD
• Implications of Higgs Searches on the Four Generation Standard Model
• Through the Looking-Glass: Alice's Adventures in Mirror World
• Neutron lifetime and dark decay of the neutron and hydrogen
• Flavour structure, flavour symmetry and supersymmetry
• Weak Mixing Angles as Dynamical Degrees of Freedom
• Supersymmetric SO(10) for fermion masses and mixings: rank-1 structures of flavour

Cited by in corpus (89)

• Radiative Corrections to Neutron and Nuclear Beta Decays Revisited
• Global Fit to Modified Neutrino Couplings and the Cabibbo-Angle Anomaly
• Beta decays as sensitive probes of lepton flavor universality
• Consequences of chirally enhanced explanations of $(g-2{)}_{\mu }$ for $h\to \mu \mu$ and $Z\to \mu \mu$
• Scrutinizing CKM unitarity with a new measurement of the $K_{\mu 3}/K_{\mu 2}$ branching fraction
• Complete Vector-like Fourth Family and new $\mathrm{U}(1{)}^{\prime }$ for Muon Anomalies
• The Fermi constant from muon decay versus electroweak fits and CKM unitarity
• Cabibbo anomaly versus electroweak precision tests: An exploration of extensions of the Standard Model
• Explaining $b\to s{\ell }^{+}{\ell }^{-}$ and the Cabibbo Angle Anomaly with a Vector Triplet
• On the Statistical Treatment of the Cabibbo Angle Anomaly
• New high-sensitivity searches for neutrons converting into antineutrons and/or sterile neutrons at the European Spallation Source
• Combined Constraints on First Generation Leptoquarks
• Searching for Lepton Flavour (Universality) Violation and Collider Signals from a Singly-Charged Scalar Singlet
• Are the CKM anomalies induced by vector-like quarks? Limits from flavor changing and Standard Model precision tests
• First-Generation New Physics in Simplified Models: From Low-Energy Parity Violation to the LHC
• Addressing the CKM Unitarity Problem with a Vector-like Up Quark
• Vector-like Singlet Quarks: a Roadmap
• A Minimal Explanation of Flavour Anomalies: B-Meson Decays, Muon Magnetic Moment, and the Cabibbo Angle
• Unveiling Hidden Physics at the LHC
• Global Analysis of Leptophilic Z' Bosons
• 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
• Anomalies in Particle Physics
• Large $t\to cZ$ as a Sign of Vector-Like Quarks in Light of the $W$ Mass
• Global Fit of Modified Quark Couplings to EW Gauge Bosons and Vector-Like Quarks in Light of the Cabibbo Angle Anomaly
• Muon $g-2$ and CKM Unitarity in Extra Lepton Models
• Update on $|V_{us}|$ and $|V_{us}/V_{ud}|$ from semileptonic kaon and pion decays
• A low-energy perspective on the minimal left-right symmetric model
• Vector-like Quark Interpretation for the CKM Unitarity Violation, Excess in Higgs Signal Strength, and Bottom Quark Forward-Backward Asymmetry
• Complete Lagrangian and Set of Feynman Rules for Scalar Leptoquarks
• Experimental Search for Neutron to Mirror Neutron Oscillations as an Explanation of the Neutron Lifetime Anomaly
• High-precision determination of the $K_{e3}$ radiative corrections
• The Forward-Backward Asymmetry in $B\to D^{\ast }\ell \nu$: One more hint for Scalar Leptoquarks?
• Ab-initio electroweak corrections to superallowed $\beta$ decays and their impact on $V_{ud}$
• New method for calculating electromagnetic effects in semileptonic beta-decays of mesons
• A possible shortcut for neutron-antineutron oscillation through mirror world
• Charged lepton flavor violation in light of the muon magnetic moment anomaly and colliders
• An $\text{ab initio}$ strategy for taming nuclear-structure dependence of $V_{ud}$ extractions: the ${}^{10}\mathrm{C}\to {}^{10}\mathrm{B}$ superallowed transition
• Radiative corrections to superallowed $\beta$ decays in effective field theory
• Radiative corrections to semileptonic beta decays: Progress and challenges
• A bridge to new physics: proposing new -- and reviving old -- explanations of $a_{\mu }$
• Asymmetry in flavour changing electromagnetic transitions of vector-like quarks
• The Impact of Different Parameterizations on the Interpretation of CP Violation in Neutrino Oscillations
• $B$ anomalies under the lens of electroweak precision
• Correlating Non-Resonant Di-Electron Searches at the LHC to the Cabibbo-Angle Anomaly and Lepton Flavour Universality Violation
• Renormalizable Models of Flavor-Specific Scalars
• The Singly-Charged Scalar Singlet as the Origin of Neutrino Masses
• $CP$ asymmetries in the rare top decays $t\to c\gamma$ and $t\to cg$
• One colorful resolution to the neutrino mass generation, three lepton flavor universality anomalies, and the Cabibbo angle anomaly
• The role of non-universal $Z$ couplings in explaining the $V_{us}$ anomaly
• Addendum to: Combined Constraints on First Generation Leptoquarks
• Next-to-Leading-Order QCD Matching for $\Delta F=2$ Processes in Scalar Leptoquark Models
• Minimal model for the $W$-boson mass, $(g-2{)}_{\mu }$, $h\to {\mu }^{+}{\mu }^{-}$ and quark-mixing-matrix unitarity
• Flavor constraints for a Vector-like quark of Nelson-Barr type
• How does Clifford algebra show the way to the second quantized fermions with unified spins, charges and families, and with vector and scalar gauge fields beyond the {\it standard model}
• Constraining $|V_{cs}|$ and physics beyond the Standard Model from exclusive (semi)leptonic charm decays
• Decays of the Heavy Top and New Insights on ${\epsilon }_K$ in a one-VLQ Minimal Solution to the CKM Unitarity Problem
• Composite Dark Matter and a horizontal symmetry
• High-Precision Branching Ratio Measurement and Spin Assignment Implications for ${}^{62}$Ga Superallowed $\beta$ Decay
• A decay microscope for trapped neon isotopes
• Branching fractions and polarizations of $D\to V(\omega ,\rho ,K^{\ast })\ell {\nu }_{\ell }$ within QCD LCSR
• $Z$ mediated Flavour Changing Neutral Currents with a Fourth Vector-Like Family
• Gauging lepton flavor SU(3) for the muon $g-2$
• Search for vector-like leptons coupling to first- and second-generation Standard Model leptons in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• A model with vectorlike fermions and $U(1{)}_X$ symmetry: CKM unitarity, $b\to s$ transitions, and prospect at Belle II
• MeV Sterile Neutrino in light of the Cabibbo-Angle Anomaly
• Theoretical point of view on Cabibbo angle anomaly
• CP-odd and CP-even Weak-Basis Invariants in the Presence of Vector-Like Quarks
• Modified lepton couplings and the Cabibbo-angle anomaly
• Gauge $SU(2{)}_f$ flavour transfers
• Vector-like quark doublets, weak-basis invariants and CP violation
• A New Neutron Lifetime Experiment with Cold Neutron Beam Decay in Superfluid Helium-4
• Improved $K_{e3}$ radiative corrections sharpen the $K_{\mu 2}$--$K_{l3}$ discrepancy
• Exploring vector-like $B$-quark pair production at CLIC in fully hadronic final states
• Vector-like Leptons in Light of the Cabibbo-Angle Anomaly
• Testing the CKM unitarity at high energy via the $W^{+}{W}^{-}$ production at the LHC and future colliders
• Perturbative unitarity constraints on generic Yukawa interactions
• The third family quark mass hierarchy and FCNC in the universal seesaw model
• Explaining the Cabibbo Angle Anomaly and Lepton Flavour Universality Violation in Tau Decays With a Singly-Charged Scalar Singlet
• Particles in finite volumes and a toy model of decaying neutrons
• Chirality structure of vector like new physics operators in charged current transitions
• A novel technique of extracting UCN lifetimes from storage bottle measurements dominated by scattering losses
• Electron Mass Singularities in Semileptonic Kaon Decays
• Complete one-loop QED corrections to $D_s^{+}$ leptonic decays and impact on the CKM unitarity test
• The Deconstruction of Flavor in the Privately Democratic Higgs Sector
• Do the Small Numbers in the Quark Mixing arise from New Physics?
• Aligned Zee-Grimus-Neufeld model for $(g-2{)}_{\mu }$
• Modelling the inverse Zeno effect for the neutron decay
• The effects of polarization on the observables in the decay ${\Xi }_{cc}^{++}\to {\Xi }_c^{+}\bar{\ell }{\nu }_{\ell }$
• Pion $\beta$ decay and $\tau \to \pi \pi {\nu }_{\tau }$ beyond leading logarithms