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FCNC Effects in a Minimal Theory of Fermion Masses
High Energy Physics - Phenomenology · Submitted 18 May 2011
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim Particularly stringent bounds, in a few TeV range, come from the corrections to the Z couplings.
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The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
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The abstract, sentence by sentence
As a minimal theory of fermion masses we extend the SM by heavy vectorlike fermions, with flavor-anarchical Yukawa couplings, that mix with chiral fermions such that small SM Yukawa couplings arise from small mixing angles. This model can be regarded as an effective description of the fermionic sector of a large class of existing flavor models and thus might serve as a useful reference frame for a further understanding of flavor hierarchies in the SM. Already such a minimal framework gives rise to FCNC effects through exchange of massive SM bosons whose couplings to the light fermions get modified by the mixing. We derive general formulae for these corrections and discuss the bounds on the heavy fermion masses. Particularly stringent bounds, in a few TeV range, come from the corrections to the Z couplings.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | As a minimal theory of fermion masses we extend the SM by heavy vectorlike fermions, with flavor-anarchical Yukawa couplings, that mix with chiral fermions such that small SM Yukawa couplings arise from small mixing angles. | contribution 0.62 | 0.67 | 0.11 | asserted 0.99 |
| s1 | This model can be regarded as an effective description of the fermionic sector of a large class of existing flavor models and thus might serve as a useful reference frame for a further understanding of flavor hierarchies in the SM. | interpretation 0.81 | 0.15 | 0.07 | hedged possibility 0.51 |
| s2 | Already such a minimal framework gives rise to FCNC effects through exchange of massive SM bosons whose couplings to the light fermions get modified by the mixing. | result 0.85 | 0.44 | 0.31 | asserted 0.98 |
| s3 | We derive general formulae for these corrections and discuss the bounds on the heavy fermion masses. | contribution 0.85 | 0.94 | 0.11 | asserted 0.98 |
| s4 | Particularly stringent bounds, in a few TeV range, come from the corrections to the Z couplings. | result 1.00 | 0.84 | 0.43 | asserted 0.99 |
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The paper
Original abstract
As a minimal theory of fermion masses we extend the SM by heavy vectorlike fermions, with flavor-anarchical Yukawa couplings, that mix with chiral fermions such that small SM Yukawa couplings arise from small mixing angles. This model can be regarded as an effective description of the fermionic sector of a large class of existing flavor models and thus might serve as a useful reference frame for a further understanding of flavor hierarchies in the SM. Already such a minimal framework gives rise to FCNC effects through exchange of massive SM bosons whose couplings to the light fermions get modified by the mixing. We derive general formulae for these corrections and discuss the bounds on the heavy fermion masses. Particularly stringent bounds, in a few TeV range, come from the corrections to the Z couplings.
Human review
References
How the literature uses it
25 arXiv papers cite this in 39 sentences
Papers citing it · 28 sentences without a confident label
Uses its data or values 3 papers
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In the $b→s$ case, a global analysis of inclusive and exclusive $b→sℓ^+ℓ^-$ decays [ref] finds $|δg_Zbs^L,R|≲8×10^-5$, while in the $s→d$ case, one finds $|δg_Zsd^L,R|≲6×10^-7$ from the $K_L→μ^+μ^-$ decay [ref] [The decay $K^+→π^+νν̅$ leads to a bound $|δg_Zsd^L,R|≲3 ×10^-6$ at 95% C.L. and is thus currently weaker than $K_L→μ^+μ^-$, even though it is theoretically much cleaner.].
A 125 GeV composite Higgs boson versus flavour and electroweak precision tests · Flavour-changing $Z$ couplings · 0.99
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In the $b→s$ case, a global analysis of inclusive and exclusive $b→sℓ^+ℓ^-$ decays [ref] finds $|δg_Zbs^L,R|≲8×10^-5$, while in the $s→d$ case, one finds $|δg_Zsd^L,R|≲6×10^-7$ from the $K_L→μ^+μ^-$ decay [ref] .[The decay $K^+→π^+νν̅$ leads to a bound $|δg_Zsd^L,R|≲3 ×10^-6$ at 95% C.L. and is thus currently weaker than $K_L→μ^+μ^-$, even though it is theoretically much cleaner.] Using ([ref]) one finds that the resulting constraints on the left-handed coupling are comparable for $b→s$ and $s →d$.
Implications of the discovery of a Higgs boson with a mass of 125 GeV · Flavour-changing $Z$ couplings · 0.96
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In the $b→s$ case, a global analysis of inclusive and exclusive $b→sℓ^+ℓ^-$ decays [ref] finds $|δg_Zbs^L,R|≲8×10^-5$, while in the $s→d$ case, one finds $|δg_Zsd^L,R|≲6×10^-7$ from the $K_L→μ^+μ^-$ decay [ref] [The decay $K^+→π^+νν̅$ leads to a bound $|δg_Zsd^L,R|≲3 ×10^-6$ at 95% C.L. and is thus currently weaker than $K_L→μ^+μ^-$, even though it is theoretically much cleaner.].
Flavour and Higgs physics near the Fermi scale · Flavour-changing $Z$ couplings · 0.99
Cites it as support 1 paper
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As shown in [ref] for such values of $M$ the model is also consistent with electroweak constraints.
Particle-Antiparticle Mixing, CP Violation and Rare K and B Decays in a Minimal Theory of Fermion Masses · Procedure in the Trivially Unitary Model · 0.99
Cites it as background 6 papers
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In a “minimal theory of fermion masses" (MTFM) [ref] the fermionic content of the SM is extended by heavy vectorlike fermions, with flavor-anarchical Yukawa couplings, that mix with SM chiral quarks.
Particle-Antiparticle Mixing, CP Violation and Rare K and B Decays in a Minimal Theory of Fermion Masses · Introduction · 0.97
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We defer to later work a detailed analysis of the phenomenological consequences for flavour violating as well as flavour conserving observables, as done e.g. in [ref] in the general case and in [ref] for the $U(3)^3$ case.
Flavour physics from an approximate U(2)^3 symmetry · Summary and outlook · 0.81
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For general investigations on vector-like fermions we refer to Refs. [ref] .
From Higgs physics to lepton flavour violation: current bounds and future prospects for vector-like lepton models · Introduction · 0.99
What it cites · 16 sentences without a confident label
Uses the method or tool of 1 paper
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Then we use the results of Ref. [ref] to fit quark masses at 1 TeV by certain powers of $$ (which are not uniquely determined since $$ is not particularly small).
Updated Values of Running Quark and Lepton Masses · Phenomenology · 0.85
Uses data or values from 1 paper
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Constraints on $K_L →μ^+ μ^-$ require $|δg_L,R^ds| ≤6 ×10^-7$ as we found using the upper bound in Ref. [ref] .
On the short-distance constraints from K_{L,S} -> mu^+ mu^- · Phenomenology · 0.96
Compares with 2 papers
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In Ref. [ref] the bounds on heavy fermion masses have been obtained from tree-level higgs exchange contributions to the FCNC processes, for flavour violating couplings to the higgs boson corresponding to our general case with $γ0$.
Composite Higgs-Mediated FCNC · Connection to Existing Models · 0.92
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Let us now compare our results for heavy fermions with the studies that have been done in the context of composite higgs models [ref] .
Warped/Composite Phenomenology Simplified · Connection to Existing Models · 0.96
Cites as background 6 papers
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Lagrangian ([ref]) has been widely used as a simplified formulation [ref] for the fermionic sector of composite Higgs models [ref] that are dual to certain warped 5d models [ref] .
Higgs as a Holographic Pseudo-Goldstone Boson · Connection to Existing Models · 0.92
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Lagrangian ([ref]) has been widely used as a simplified formulation [ref] for the fermionic sector of composite Higgs models [ref] that are dual to certain warped 5d models [ref] .
Warped/Composite Phenomenology Simplified · Connection to Existing Models · 0.92
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Several theoretical ideas have been proposed to explain the peculiar pattern of fermion masses and mixings, such as horizontal symmetries [ref] , fermion localization in extra dimensional models of Randall–Sundrum (RS) type [ref] or wave function renormalization (WFR) [ref] by new strong interactions [ref] .
Should Squarks Be Degenerate? · Introduction · 0.98
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