Baryogenesis from combined Higgs - scalar field inflation

TL;DR

This paper proposes a modified Higgs inflation model with an extra scalar field that can produce helical magnetic fields, address the baryon asymmetry, and solve the Standard Model instability, with testable collider signatures.

Contribution

It introduces a combined Higgs-scalar inflation scenario with a CP-odd operator that generates magnetic fields and baryogenesis, and predicts collider signatures for the scalar.

Findings

The model aligns with cosmological observations from Planck/BICEP/Keck.

It identifies a parameter window where magnetic fields survive constraints and generate baryon asymmetry.

The scalar can be detected at colliders with mass bounds from ATLAS and CMS.

Abstract

We study a modification of the Higgs inflation scenario where we introduce an extra scalar $\phi$, with mass $m$, coupled to the Ricci scalar as $g\phi^2 R$, and mixed with the Higgs field $h$ via the Lagrangian term $\mu \phi h^2$. Both fields participate in the inflation process in a unitary theory that predicts values of the cosmological observables in agreement with the results from the Planck/BICEP/Keck collaborations. In addition, by means of a $\mathcal{CP}$-odd effective operator that couples $\phi$ to the Chern-Simons term of the hypercharge gauge group as $f_\phi^{-1}\phi \,Y_{\mu\nu}\tilde Y^{\mu\nu}$, maximally helical magnetic fields are produced during the last $e$-folds of inflation. We found a window in the coupling $ f_\phi$ where these fields survive all constraints until the electroweak phase transition, and source the baryon asymmetry of the Universe through the Standard Model chiral anomaly. From a phenomenological perspective, the model can solve the Standard Model instability problem at the scale $\mathcal Q_I\simeq 10^{11}$ GeV, provided that $\mu\lesssim m \lesssim \mathcal Q_I$, and for $m\lesssim \mathcal{O}$(few)~TeV, the $\phi$-$h$ mixing becomes sizable while the theory turns natural. The latter thus predicts modifications of the trilinear and quartic couplings that could be explored at the HE-LHC, as well as at future colliders, and allows for direct $\phi$ production at the LHC followed by decay into $hh$. Present results from ATLAS and CMS already put (mild) bounds on the mass of the heavy scalar as $m\gtrsim 0.55$~TeV at 95\% C.L.