We build a model of lepton flavor in a slice of AdS5. We add to the 5D SM fields a set of neutrino fields, as well as a horizontal U(1) symmetry and a flavon field, all propagating in the bulk. The electroweak and U(1) symmetries are spontaneously broken by a potential localized on the infrared boundary. We show that in a flavor anarchic scenario, by suitable choice of the 5D masses and the U(1) charges, the masses of the SM leptons and the PMNS matrix can be naturally generated. The neutrino masses are Dirac like, with a normal ordered hierarchical spectrum, <InlineEquation ID="IEq1"> <EquationSource Format="MATHML"><math display="inline"> <mtext>∆</mtext> <msubsup> <mi>m</mi> <mn>32</mn> <mn>2</mn> </msubsup> <mo>≈</mo> <msubsup> <mi>m</mi> <mn>3</mn> <mn>2</mn> </msubsup> <mo>,</mo> <mtext>∆</mtext> <msubsup> <mi>m</mi> <mn>21</mn> <mn>2</mn> </msubsup> <mo>≈</mo> <msubsup> <mi>m</mi> <mn>2</mn> <mn>2</mn> </msubsup> <mo>≫</mo> <msubsup> <mi>m</mi> <mn>1</mn> <mn>2</mn> </msubsup> </math></EquationSource> <EquationSource Format="TEX">$ \Delta {m}_{32}^2\approx {m}_3^2,\Delta {m}_{21}^2\approx {m}_2^2\gg {m}_1^2 $</EquationSource> </InlineEquation>, and a suppressed θ13 mixing angle. We find configurations where the charged lepton mixing angles are suppressed by powers of the Cabibbo angle (λC) relative to vanilla anarchic partial compositeness, consequently reducing CP and lepton flavor violation. Specifically, the Wilson coefficient for the electron electromagnetic dipole moment exhibits <InlineEquation ID="IEq2"> <EquationSource Format="MATHML"><math display="inline"> <msubsup> <mi>λ</mi> <mi>C</mi> <mn>2</mn> </msubsup> </math></EquationSource> <EquationSource Format="TEX">$ {\lambda}_C^2 $</EquationSource> </InlineEquation> suppression, while those governing μ → eγ and μ − e vector operators are suppressed by <InlineEquation ID="IEq3"> <EquationSource Format="MATHML"><math display="inline"> <msubsup> <mi>λ</mi> <mi>C</mi> <mrow> <mn>3</mn> <mo>/</mo> <mn>2</mn> </mrow> </msubsup> </math></EquationSource> <EquationSource Format="TEX">$ {\lambda}_C^{3/2} $</EquationSource> </InlineEquation> compared to the anarchic scenario without U(1) horizontal symmetry.

Lepton flavor from a horizontal symmetry in a slice of AdS₅

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2026年5月19日

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Leandro Da Rold,
Franco A. Gigena,
Jaime S. Guzmán Guerrero

摘要

We build a model of lepton flavor in a slice of AdS₅. We add to the 5D SM fields a set of neutrino fields, as well as a horizontal U(1) symmetry and a flavon field, all propagating in the bulk. The electroweak and U(1) symmetries are spontaneously broken by a potential localized on the infrared boundary. We show that in a flavor anarchic scenario, by suitable choice of the 5D masses and the U(1) charges, the masses of the SM leptons and the PMNS matrix can be naturally generated. The neutrino masses are Dirac like, with a normal ordered hierarchical spectrum, $∆ m_{32}^{2} \approx m_{3}^{2}, ∆ m_{21}^{2} \approx m_{2}^{2} ≫ m_{1}^{2}$ $ \Delta {m}_{32}^2\approx {m}_3^2,\Delta {m}_{21}^2\approx {m}_2^2\gg {m}_1^2 $ , and a suppressed θ₁₃ mixing angle. We find configurations where the charged lepton mixing angles are suppressed by powers of the Cabibbo angle (λ_C) relative to vanilla anarchic partial compositeness, consequently reducing CP and lepton flavor violation. Specifically, the Wilson coefficient for the electron electromagnetic dipole moment exhibits $λ_{C}^{2}$ $ {\lambda}_C^2 $ suppression, while those governing μ → eγ and μ − e vector operators are suppressed by $λ_{C}^{3 / 2}$ $ {\lambda}_C^{3/2} $ compared to the anarchic scenario without U(1) horizontal symmetry.

Lepton flavor from a horizontal symmetry in a slice of AdS5

摘要

Lepton flavor from a horizontal symmetry in a slice of AdS₅