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

Abstract

Non-supersymmetric Grand Unified SO(10) × U(1) PQ models have all the ingredients to solve several fundamental problems of particle physics and cosmologyneutrino masses and mixing, baryogenesis, the non-observation of strong CP violation, dark matter, inflation -in one stroke. The axion -the pseudo Nambu-Goldstone boson arising from the spontaneous breaking of the U(1) PQ Peccei-Quinn symmetry -is the prime dark matter candidate in this setup. We determine the axion mass and the low energy couplings of the axion to the Standard Model particles, in terms of the relevant gauge symmetry breaking scales. We work out the constraints imposed on the latter by gauge coupling unification. We discuss the cosmological and phenomenological implications.

Several Problems in Particle Physics and Cosmology Solved in One SMASH

“…Therefore, this model is more predictive in the axion sector than SMASH or 2hdSMASH, yet less predictive than miniSU(5)PQ due to the additional freedom inherent in having a multi-step breaking of the grand unified group -as opposed to the single-step breaking in the SU(5) case-as well as due to the additional threshold corrections that can arise from the greater number of particles included in the SO(10) multiplets. Allowing for a reasonable range of scalar threshold corrections and taking into account constraints from black hole superradiance [75] and proton decay, the axion decay constant and mass is predicted to lie in the range [20] 2.6 × 10 15 GeV < f A < 3.0 × 10 17 GeV, 1.9 × 10 −11 eV < m A < 2.2 × 10 −9 eV.…”

“…The smallness of the axion mass in this model implies that the axion can be identified with dark matter only if the Peccei-Quinn symmetry is broken before or during inflation and not Table 4. Axion predictions in SU (5) × U (1) PQ [58] and SO(10) × U (1) PQ models [20]: Axion decay constant f A , domain wall number N DW , coupling to the photon C Aγ , and tree-level couplings to quarks and charged leptons C Ai , i = u, ..., t, e, .., τ . In the SU (5) theory, tan β = v H /v H , while for the SO(10) Table 5.…”

“…In the SU (5) theory, tan β = v H /v H , while for the SO(10) Table 5. Field content and PQ charge assignments in two distinct SO(10) × U (1) PQ models [20].…”

“…Unfortunately, the minimal PQ symmetry (24) leads to a decay constant f A = v/3 [20,[72][73][74], which is clearly experimentally excluded. The simplest way to remedy this problem is to associate a PQ charge also to the 210 H ,…”

“…[16,17]. These obstacles of the νMSM can be neatly circumvented in SMASH-type [18][19][20] extensions of the SM which are built around the axion for the solution of the strong CP problem [21][22][23], as well as for dark matter, and allow inflation to be driven by (a mixture of the modulus of the Higgs field with) the modulus of the Peccei-Quinn field -sometimes called saxion field [24,25].…”