Axion-Higgs unification

Abstract

Abstract In theories with no fundamental scalars, one gauge group can become strong at a large scale Λ and spontaneously break a global symmetry, producing the Higgs and the axion as composite pseudo-Nambu-Goldstone bosons. We show how KSVZ and DFSZ axion models can be naturally realised. The assumption Λ ≈ 1011 GeV is phenomenologically favoured because: a) The axion solves the QCD θ problem and provides the observed DM abundance; b) The observed Higgs mass is generated via RGE effects from a small Higgs quartic coupling at the compositeness scale, provided that the Higgs mass term is fine-tuned to be of electroweak size; c) Lepton, quark as well as neutrino masses can be obtained from four-fermion operators at the compositeness scale. d) Extra fermions can unify the gauge couplings.