INFLAVON: CMB as cosmic tracer of Flavor physics

TL;DR

This paper links flavor physics and cosmic inflation by proposing the flavon field as the inflaton, analyzing its cosmological signatures, and exploring its potential as dark matter within Froggatt-Nielsen models.

Contribution

It introduces the inflavon concept, unifying flavor symmetry breaking with inflation, and provides CMB predictions to test this novel framework.

Findings

Identifies parameter regions consistent with current CMB data.

Predicts observable signatures for next-generation CMB experiments.

Discusses inflavon as a dark matter candidate with isocurvature constraints.

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 $\alpha$-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 $\Lambda_{\rm FN}$ 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.