Abstract
We propose a model for the QCD axion which is realized through a coupling of the Peccei-Quinn scalar field to magnetically charged fermions at high energies. We show that the axion of this model solves the strong CP problem and then integrate out heavy magnetic monopoles using the Schwinger proper time method. We find that the model discussed yields axion couplings to the Standard Model which are drastically different from the ones calculated within the KSVZ/DFSZ-type models, so that large part of the corresponding parameter space can be probed by various projected experiments. Moreover, the axion we introduce is consistent with the astrophysical hints suggested both by anomalous TeV-transparency of the Universe and by excessive cooling of horizontal branch stars in globular clusters. We argue that the leading term for the cosmic axion abundance is not changed compared to the conventional pre-inflationary QCD axion case for axion decay constant fa> 1012 GeV.
Highlights
KSVZ [9, 10] and DFSZ [11, 12] axion models were constructed, which were called invisible, because interactions of the corresponding axion particles with the Standard Model (SM) are very faint
We find that the model discussed yields axion couplings to the Standard Model which are drastically different from the ones calculated within the KSVZ/DFSZ-type models, so that large part of the corresponding parameter space can be probed by various projected experiments
Appeal of the invisible models is their simplicity: the DFSZ model exploits the 2HDM just as in the case of the PQWW axion but the axion is identified with the phase of a new SM-singlet complex scalar field which couples to the Higgses at high energies; while the KSVZ model exploits coupling of a new SMsinglet complex scalar field, the phase of which is identified with the axion, to a new heavy quark
Summary
As it was shown by Dirac [19], the observed quantization of charge in electrodynamics can be elegantly explained by adding a magnetic monopole to the theory. Failure of our perturbative techniques does not mean that the theory is by itself inconsistent and it was formally shown by Brandt, Neri and Zwanziger [21, 22] using the path-integral approach that observables of the Zwanziger theory are Lorentz invariant if the Dirac condition (2.1) is satisfied Note that this analysis was performed both in the case where electric and magnetic particles are complex scalars as well as in the case where they are all Dirac fermions. Let us note, that non-Abelian magnetic charges are often introduced as emergent from spontaneous breaking of some larger gauge symmetry, the results by Goddard, Nuyts and Olive do not depend on such a construction and can be as well stated for generic magnetic monopoles defined in the fiber bundle framework of Wu and Yang [30]. Of SU(3) with the coupling constant 2π/gs , bearing in mind that the higher representation GNO monopoles are unstable due to the Brandt-Neri-Coleman analysis [31, 32]
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