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INFLAVON: CMB as cosmic tracer of Flavor physics

Mu-Chun Chen, Anish Ghoshal, V. Knapp-Perez, Xueqi Li, Xiang-Gan Liu, Cameron Moffett-Smith

Abstract

We unify one of the most widely studied frameworks to explain the hierarchical structure of the flavor sector in the Standard Model, the Froggatt-Nielsen mechanism, with cosmic inflation. We propose that the complex scalar field, the so-called flavon, which breaks the Froggatt-Nielsen $U(1)$ symmetry and generates the Yukawa couplings of the Standard Model, to also drive inflation, which we dub as Inflavon. After inflation ends, the decay of the inflavon reheats the Universe, establishing a novel link between early Universe cosmology and flavor physics. As concrete examples, we present realizations where the inflavon potential is described by an $α$-attractor potential. We then compute the resulting CMB observables, specifically the spectral index ($n_s$), the tensor-to-scalar ratio ($r$), and the amplitude of scalar perturbations ($A_s$) as functions of the underlying Froggatt-Nielsen model parameters. We identify the parameter space in Froggatt-Nielsen models involving the scale of Flavor symmetry breaking $Λ_{\rm FN}$ and FN charges which is ruled out by Planck and ACT data, as well as the region that could be probed by next-generation CMB experiments like CMB-S4, SO and LiteBIRD. We also discuss inflavon as dark matter and its isocurvature constraints.

INFLAVON: CMB as cosmic tracer of Flavor physics

Abstract

We unify one of the most widely studied frameworks to explain the hierarchical structure of the flavor sector in the Standard Model, the Froggatt-Nielsen mechanism, with cosmic inflation. We propose that the complex scalar field, the so-called flavon, which breaks the Froggatt-Nielsen symmetry and generates the Yukawa couplings of the Standard Model, to also drive inflation, which we dub as Inflavon. After inflation ends, the decay of the inflavon reheats the Universe, establishing a novel link between early Universe cosmology and flavor physics. As concrete examples, we present realizations where the inflavon potential is described by an -attractor potential. We then compute the resulting CMB observables, specifically the spectral index (), the tensor-to-scalar ratio (), and the amplitude of scalar perturbations () as functions of the underlying Froggatt-Nielsen model parameters. We identify the parameter space in Froggatt-Nielsen models involving the scale of Flavor symmetry breaking and FN charges which is ruled out by Planck and ACT data, as well as the region that could be probed by next-generation CMB experiments like CMB-S4, SO and LiteBIRD. We also discuss inflavon as dark matter and its isocurvature constraints.
Paper Structure (10 sections, 63 equations, 9 figures, 2 tables)

This paper contains 10 sections, 63 equations, 9 figures, 2 tables.

Table of Contents

  1. Introduction
  2. $\mathrm{U}(1)$ Froggatt-Nielsen models
  3. CMB imprints from $\alpha-$attractor inflaton potentials
  4. Froggatt-Nielsen faces cosmology constraints
  5. $\alpha-$attractor potentials for $n=1$
  6. $\alpha-$attractor potential for $n\neq 1$.
  7. Discussion and Conclusion
  8. Higgs-Flavon mixing
  9. $\alpha-$attractor potentials from $\mathrm{U}(1)_\mathrm{FN}$ flavon potential
  10. Reheating Temperature for $n=1$ and $n=3$

Figures (9)

  • Figure 1: The $\alpha$-attractor potentials as functions of $\frac{\chi}{\Lambda_\mathrm{flat}}$, for different values of $\alpha$ and $n$ in the E-, T-, P-models defined in \ref{['eq:alpha-attractors']}.
  • Figure 2: Results for E-Model. The solid and dashed lines are the $1-$sigma and $2-$ sigma current constraints from Planck, BK15, and ACTPlanck:2018vygBICEP2:2018kqh. The light and dark shaded regions represent future experimental constraints from LiteBIRD, CMB-S4, and SOLiteBIRD:2022cntCMB-S4:2016pleSimonsObservatory:2018koc.
  • Figure 3: Results for E-Model. The solid and dashed lines are the $1-$sigma and $2-$ sigma current constraints from Planck, BK15, and ACTPlanck:2018vygBICEP2:2018kqh. The light and dark shaded regions represent future experimental constraints from LiteBIRD, CMB-S4, and SOLiteBIRD:2022cntCMB-S4:2016pleSimonsObservatory:2018koc.
  • Figure 4: Results for T-model. The solid and dashed lines are the $1-$sigma and $2-$ sigma current constraints from Planck, BK15, and ACTPlanck:2018vygBICEP2:2018kqh. The light and dark shaded regions represent future experimental constraints from LiteBIRD, CMB-S4, and SOLiteBIRD:2022cntCMB-S4:2016pleSimonsObservatory:2018koc.
  • Figure 5: Results for T-model. The solid and dashed lines are the $1-$sigma and $2-$ sigma current constraints from Planck, BK15, and ACTPlanck:2018vygBICEP2:2018kqh. The light and dark shaded regions represent future experimental constraints from LiteBIRD, CMB-S4, and SOLiteBIRD:2022cntCMB-S4:2016pleSimonsObservatory:2018koc.
  • ...and 4 more figures