An ultra-weak sector, the strong CP problem and the pseudo-Goldstone dilaton
Kyle Allison (Department of Theoretical Physics, University of Oxford, 1 Keble Road, Oxford, OX1 3NP, United Kingdom); Christopher T. Hill (Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL, 60510, USA); Graham G. Ross (Department of Theoretical Physics, University of Oxford, 1 Keble Road, Oxford, OX1 3NP, United Kingdom)
In the context of a Coleman–Weinberg mechanism for the Higgs boson mass, we address the strong CP problem. We show that a DFSZ-like invisible axion model with a gauge-singlet complex scalar field S , whose couplings to the Standard Model are naturally ultra-weak, can solve the strong CP problem and simultaneously generate acceptable electroweak symmetry breaking. The ultra-weak couplings of the singlet S are associated with underlying approximate shift symmetries that act as custodial symmetries and maintain technical naturalness. The model also contains a very light pseudo-Goldstone dilaton that is consistent with cosmological Polonyi bounds, and the axion can be the dark matter of the universe. We further outline how a SUSY version of this model, which may be required in the context of Grand Unification, can avoid introducing a hierarchy problem.
