Standard Model—axion—seesaw—Higgs portal inflation. Five problems of particle physics and cosmology solved in one stroke

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 σ, whose vacuum expectation value v σ ∼ 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 σ 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 -seesawHiggs portal inflation (SMASH) model. It can be probed decisively by upcoming cosmic microwave background and axion dark matter experiments.

Axion predictions in SO(10) × U(1)PQ models

“…Crucially, in these extended models, the PQ symmetry breaking scale v PQ and the seesaw scale v BL are independent parameters -in fact, the axion field has to be orthogonal to the Goldstone field which is eaten by the gauge bosons getting mass by B-L breaking. This is different in the original SMASH model [1,2], where the PQ symmetry is at the same time also a B-L symmetry. for gauge coupling unification with scalar threshold corrections, we have found an upper bound on the decay-constant f A < 4.0 × 10 14 GeV, and a corresponding lower bound on the axion mass, m A > 1.4 × 10 −8 eV.…”

“…Finally, at temperatures around the QCD transition between a quark-gluon and a hadron plasma phase, dark matter is produced in the form of a condensate of extremely nonrelativistic axions [11][12][13]. To account for all of the cold dark matter in the universe, the U(1) PQ symmetry breaking scale is required to be around v σ ∼ 2 × 10 11 GeV, corresponding an axion mass around 30 µeV [1,2,14,15]. Adding a cosmological constant to account for the present acceleration of the universe, SMASH offers a self-contained description of particle physics, from the electroweak scale to the Planck scale, and of cosmology, from inflation until today.…”

“…Clearly, in order to get fermion mixing at all, one needs at least two distinctive Higgs representations. 2 Out of the six remaining combinations, however, only three turn out to give realistic fermion mass and mixing patterns: 10 H +126 H , 120 H + 126 H , and 10 H + 120 H (see for example [31,32] and references therein). From these combinations, the first two are phenomenologically preferred since the 126 H is required for neutrino mass generation via the seesaw mechanism.…”

“…Furthermore, the Hubble expansion rate during inflation must have been small, H I 10 9 GeV, to avoid constraints from the non-observation of traces of isocurvature fluctuations in the cosmic microwave background radiation [78][79][80][81]. The latter constraint disqualifies Model 1 as a possible GUT SMASH candidate, since in Higgs portal inflation the Hubble expansion rate during inflation is of order 10 13 GeV H I 10 14 GeV [2].…”

“…Employing a bottom-up approach, it has been shown recently that a minimal extension model of the SM -dubbed Standard Model-Axion -Seesaw-Higgs portal inflation model or SMASH -may explain these problems in one stroke [1,2]. It consists in extending the SM by three right-handed extra neutrinos, by an extra quark, and a complex scalar field, which are charged under a new global U(1) PQ Peccei-Quinn (PQ) symmetry.…”