Unified Theories with U(2) Flavor Symmetry

A. Romanino; L.J. Hall; R. Barbieri; S. Raby

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Unified Theories with U(2) Flavor Symmetry

R. Barbieri, L.J. Hall, S. Raby, A. Romanino

High Energy Physics - Phenomenology · Submitted 23 Oct 1996

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim A fit to the fermion mass data leads to a prediction for the angles of the CKM unitarity triangle, which will allow a significant test of these unified U(2) theories.

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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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What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.13 · human participants 0.01 · controlled comparison 0.01 · randomized assignment 0.01 · states quantitative result 0.88 · compares with prior results 0.08 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; show every role.

A general operator expansion is presented for quark and lepton mass matrices in unified theories based on a U(2) flavor symmetry, with breaking parameter of order $V_{cb} \approx m_s/m_b \approx \sqrt{m_c/m_t}$. While solving the supersymmetric flavor-changing problem, a general form for the Yukawa couplings follows, leading to 9 relations among the fermion masses and mixings, 5 of which are precise. The combination of grand unified and U(2) symmetries provides a symmetry understanding for the anomalously small values of $m_u/m_c$ and $m_c/m_t$. A fit to the fermion mass data leads to a prediction for the angles of the CKM unitarity triangle, which will allow a significant test of these unified U(2) theories. A particular SO(10) model provides a simple realization of the general operator expansion. The lighter generation masses and the non-trivial structure of the CKM matrix are generated from the exchange of a single U(2) doublet of heavy vector generations. This model suggests that CP is spontaneously broken at the unification scale --- in which case there is a further reduction in the number of free parameters.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	A general operator expansion is presented for quark and lepton mass matrices in unified theories based on a U(2) flavor symmetry, with breaking parameter of order $V_{cb} \approx m_s/m_b \approx \sqrt{m_c/m_t}$.	contribution 0.96	0.86	0.13	asserted 1.00
s1	While solving the supersymmetric flavor-changing problem, a general form for the Yukawa couplings follows, leading to 9 relations among the fermion masses and mixings, 5 of which are precise.	result 0.88	0.85	0.30	asserted 1.00
s2	The combination of grand unified and U(2) symmetries provides a symmetry understanding for the anomalously small values of $m_u/m_c$ and $m_c/m_t$.	interpretation 0.88	0.69	0.16	asserted 1.00
s3	A fit to the fermion mass data leads to a prediction for the angles of the CKM unitarity triangle, which will allow a significant test of these unified U(2) theories.	result 0.83	0.87	0.30	asserted 0.82
s4	A particular SO(10) model provides a simple realization of the general operator expansion.	contribution 0.51	0.70	0.05	asserted 0.99
s5	The lighter generation masses and the non-trivial structure of the CKM matrix are generated from the exchange of a single U(2) doublet of heavy vector generations.	method 0.44	0.59	0.14	asserted 0.99
s6	This model suggests that CP is spontaneously broken at the unification scale --- in which case there is a further reduction in the number of free parameters.	interpretation 0.92	0.55	0.13	hedged possibility 1.00

What kind of paper the classifier reports this is: theoretical result 1.00 · evidence from proof or derivation 0.77.

What was examined, and what was not

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arXiv listing abstract v1

not examined

full text
figures and tables
references and citing sentences
relations to other papers

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P abstract

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S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

The paper

Original abstract

A general operator expansion is presented for quark and lepton mass matrices in unified theories based on a U(2) flavor symmetry, with breaking parameter of order $V_{cb} \approx m_s/m_b \approx \sqrt{m_c/m_t}$. While solving the supersymmetric flavor-changing problem, a general form for the Yukawa couplings follows, leading to 9 relations among the fermion masses and mixings, 5 of which are precise. The combination of grand unified and U(2) symmetries provides a symmetry understanding for the anomalously small values of $m_u/m_c$ and $m_c/m_t$. A fit to the fermion mass data leads to a prediction for the angles of the CKM unitarity triangle, which will allow a significant test of these unified U(2) theories. A particular SO(10) model provides a simple realization of the general operator expansion. The lighter generation masses and the non-trivial structure of the CKM matrix are generated from the exchange of a single U(2) doublet of heavy vector generations. This model suggests that CP is spontaneously broken at the unification scale --- in which case there is a further reduction in the number of free parameters.

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References

Forward citations

Cited by 11 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Hierarchies from Higher Flavor Spin
hep-ph 2026-05 unverdicted novelty 7.0 of 10

Yukawa hierarchies are generated from powers of fully anarchic spurions in higher SU(2) and SU(3) flavor representations via progressive rank lifting through composite outer products, with explicit models and predicti...
Flavor hierarchies with nonminimal irreducible representations
hep-ph 2025-10 unverdicted novelty 7.0 of 10

Introduces a new class of flavor models using non-minimal irreducible representations for the flavor-breaking spurion to generate fermion mass hierarchies accidentally from O(1) UV parameters via multiple insertions, ...
Probing Lepton Flavor Violation at FCC-ee
hep-ph 2026-10 accept novelty 6.0 of 10

At FCC-ee, tau lepton decays into three leptons or a lepton and a photon can detect lepton flavor violation with greater sensitivity than Z boson decays, and can complement Higgs boson decays depending on the new phys...
The Very Nearly Right Theory of Flavor
hep-ph 2026-07 conditional novelty 6.0 of 10

A systematic scan of all nine-link Yukawa textures shows the quark CP phase clusters at pi/8, pi/4, pi/2, 3pi/8, and yields precise, falsifiable predictions for the CKM unitarity triangle angles.
New Physics and CP Violation in Singly Cabibbo Suppressed D Decays
hep-ph 2006-09 conditional novelty 6.0 of 10

Percent-level CP asymmetries in singly Cabibbo suppressed D decays would signal new physics, and supersymmetric left-right squark mixing can generate them without violating mixing bounds.

Show 6 more citing papers

Quark Mass Ratios and Mixing Angles from SU(3) Family Gauge Symmetry
hep-ph 2006-03 conditional novelty 6.0 of 10

An SU(3) family gauge model reproduces the quark mass hierarchy and two CKM angles from one-loop radiative corrections, while underestimating theta13.
Baryogenesis through leptogenesis
hep-ph 1999-11 conditional novelty 6.0 of 10

The lepton asymmetry in heavy-neutrino leptogenesis must be tracked as a 3x3 flavour density matrix, and with that bookkeeping both a U(1) and a U(2) family-symmetry model can be brought near the observed baryon asymmetry.
Anatomy and Phenomenology of FCNC and CPV Effects in SUSY Theories
hep-ph 2009-09 accept novelty 5.0 of 10

Correlation patterns among B, K, D and lepton observables separate supersymmetric flavour models with right-handed currents from those with left-handed currents, and both from Little-Higgs and Randall-Sundrum alternatives.
Real and Imaginary Elements of Fermion Mass Matrices
hep-ph 2006-03 conditional novelty 5.0 of 10

Two five-parameter quark mass textures with only real or imaginary entries, selected because alpha is nearly 90 degrees, reproduce the measured quark masses and CKM mixings and predict alpha approximately equal to pi over 2.
Pieces of the Flavour Puzzle
hep-ph 2015-03 accept novelty 3.0 of 10

The review argues that fermion masses and mixing angles can be organized by a single map with order-one inputs, realizable in many frameworks including SU(5) and SO(10) unification, but that no compelling symmetry pri...
Discrete Flavor Symmetries and Models of Neutrino Mixing
hep-ph 2010-02 accept novelty 1.0 of 10

A review of how A4, S4, and related discrete flavor groups can produce tri-bimaximal neutrino mixing at leading order, with small calculable corrections and testable predictions for theta13 and lepton flavor violation.

How the literature uses it

35 arXiv papers cite this in 46 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 25 sentences without a confident label

Compares with it 1 paper

Let us contrast this with existing implementations of $U(2)$ breaking [ref] , which generate the flavor structure of the light families.

Hierarchies from Higher Flavor Spin · Introduction · 0.91

Cites it as background 18 papers

To achieve this goal, we consider four basic hypotheses about the flavour structure of the soft-breaking terms: the Minimal Flavour Violation (MFV) hypothesis [ref] , a chiral $U(2)$ flavour symmetry [ref] , a $U(1)$ symmetry a la Froggatt-Nielsen [ref] , and finally the framework of disoriented $A$ terms [ref] .

Exploring the flavour structure of the high-scale MSSM · Introduction · 0.83
Representative examples with $n_2=1$ and $n_3=0$ include $U(2)_all$ [ref] , $U(2)_ψ_L=q+ℓ$ [ref] , $U(2)_q+e^(c)$ and $U(2)_10 ×Z_2$ [ref] , as well as constructions such as $MFP=SU(2)_q ×U(1)_X$ [ref] and $SU(2)_all ×U(1)_F$ [ref] .

Hierarchies from Higher Flavor Spin · Introduction · 0.88
In contrast to abelian models, where there is a lot of freedom in fixing the charges of the SM fermions under the flavour symmetry, non-abelian models [ref] are quite predictive for fermion mass matrices once the pattern of symmetry breaking is specified.

Anatomy and Phenomenology of FCNC and CPV Effects in SUSY Theories · Non-abelian Flavour Models · 0.93

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