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Linking Axions, the Flavor Problem, and Neutrino Masses through a Flavored Peccei-Quinn Symmetry

Yithsbey Giraldo, Eduardo Rojas, Juan C. Salazar

Abstract

Recent measurements by several experimental collaborations have reported deviations from Standard Model (SM) predictions in diphoton final states, potentially hinting at the existence of intermediate scalar resonances above the electroweak scale. Such anomalies can be naturally accommodated within SM extensions featuring an enlarged scalar sector. In particular, multi-Higgs doublet frameworks arise in Flavored Axion Models (FAMs), which have been proposed to explain the texture zeros of quark mass matrices. These models provide a unified description of quark masses and the Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix while simultaneously addressing the strong CP problem. In this work we study a concrete FAM realization augmented with Majorana masses for right-handed neutrinos, implementing a type-I seesaw mechanism. In this model the flavor structure is effectively determined by the vacuum expectation values of the scalar doublets and Yukawa couplings of order one. Within this framework, neutrino and axion mass scales are intrinsically connected, as the heavy right-handed neutrinos obtain their masses from the scalar field responsible for the spontaneous breaking of the Peccei-Quinn symmetry. We further explore the phenomenological implications of the model, including constraints from flavor-changing neutral currents derived from semileptonic decays, as well as current experimental limits on the axion-photon coupling obtained from axion search experiments.

Linking Axions, the Flavor Problem, and Neutrino Masses through a Flavored Peccei-Quinn Symmetry

Abstract

Recent measurements by several experimental collaborations have reported deviations from Standard Model (SM) predictions in diphoton final states, potentially hinting at the existence of intermediate scalar resonances above the electroweak scale. Such anomalies can be naturally accommodated within SM extensions featuring an enlarged scalar sector. In particular, multi-Higgs doublet frameworks arise in Flavored Axion Models (FAMs), which have been proposed to explain the texture zeros of quark mass matrices. These models provide a unified description of quark masses and the Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix while simultaneously addressing the strong CP problem. In this work we study a concrete FAM realization augmented with Majorana masses for right-handed neutrinos, implementing a type-I seesaw mechanism. In this model the flavor structure is effectively determined by the vacuum expectation values of the scalar doublets and Yukawa couplings of order one. Within this framework, neutrino and axion mass scales are intrinsically connected, as the heavy right-handed neutrinos obtain their masses from the scalar field responsible for the spontaneous breaking of the Peccei-Quinn symmetry. We further explore the phenomenological implications of the model, including constraints from flavor-changing neutral currents derived from semileptonic decays, as well as current experimental limits on the axion-photon coupling obtained from axion search experiments.
Paper Structure (19 sections, 41 equations, 3 figures, 3 tables)

This paper contains 19 sections, 41 equations, 3 figures, 3 tables.

Table of Contents

  1. Introduction
  2. The Five texture-zero mass matrices
  3. A Realistic Texture for Quark Mass Matrices
  4. PQ symmetry and the minimal particle content
  5. Yukawa Lagrangian and the PQ symmetry
  6. Naturalness of Yukawa couplings
  7. Scalar potential
  8. Axion–Neutrino Mass Relation
  9. Low energy constraints
  10. Flavor changing neutral currents
  11. Constraints on the axion-photon coupling
  12. Haloscopes.
  13. Helioscopes.
  14. Laboratory searches.
  15. Astrophysical constraints.
  16. ...and 4 more sections

Figures (3)

  • Figure 1: To connect with current phenomenology we set $M_{H_1}=95GeV$, $M_{H_2}=125GeV$, $M_{C_1}=130GeV$. Heavier scalars span the ranges $M_{H_3}\in[200GeV,50TeV]$, $M_{C_2}\in[300GeV,300TeV]$, $M_{A_1}\in[95GeV,150GeV]$. Higher states are taken above the current LHC reach.
  • Figure 2: Allowed regions by lepton decays. For the down-type quarks and charged leptons the non-universal part of the PQ charges just depend on the diference $s_2-s_1 = N\epsilon/9$, hence the flavor-changing neutral-current couplings (the off diagonal elements) just depend on $\epsilon$.
  • Figure 3: The excluded parameter space by various experiments corresponds to the colored regions, the dashed-lines correspond to the projected bounds of coming experiments looking for axion signals AxionLimits. The gray region corresponds to the parameter space scanned by our model.