Standard Model-Axion-Seesaw-Higgs Portal Inflation. Five problems of particle physics and cosmology solved in one stroke

TL;DR

The SMASH model unifies solutions to five major problems in particle physics and cosmology, including inflation, dark matter, neutrino masses, baryogenesis, and the strong CP problem, through minimal extensions of the Standard Model.

Contribution

It introduces a minimal extension with right-handed neutrinos, a new color triplet, and a scalar to simultaneously address multiple fundamental issues in physics and cosmology.

Findings

Solves the strong CP problem with the axion.

Accounts for cold dark matter via axion.

Provides a unified inflationary scenario with testable predictions.

Abstract

We present a minimal extension of the Standard Model (SM) providing a consistent picture of particle physics from the electroweak scale to the Planck scale and of cosmology from inflation until today. Three right-handed neutrinos $N_i$, a new color triplet $Q$ and a complex SM-singlet scalar $\sigma$, whose vacuum expectation value $v_\sigma \sim 10^{11}$ GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously, are added to the SM. At low energies, the model reduces to the SM, augmented by seesaw generated neutrino masses and mixing, plus the axion. The latter solves the strong CP problem and accounts for the cold dark matter in the Universe. The inflaton is comprised by a mixture of $\sigma$ and the SM Higgs, and reheating of the Universe after inflation proceeds via the Higgs portal. Baryogenesis occurs via thermal leptogenesis. Thus, five fundamental problems of particle physics and cosmology are solved at one stroke in this unified Standard Model - Axion - seesaw - Higgs portal inflation (SMASH) model. It can be probed decisively by upcoming cosmic microwave background and axion dark matter experiments.