Abstract
We determine the model-independent component of the couplings of axions to electroweak gauge bosons, induced by the minimal coupling to QCD inherent to solving the strong CP problem. The case of the invisible QCD axion is developed first, and the impact on W and Z axion couplings is discussed. The analysis is extended next to the generic framework of heavy true axions and low axion scales, corresponding to scenarios with enlarged confining sector. The mass dependence of the coupling of heavy axions to photons, W and Z bosons is determined. Furthermore, we perform a two-coupling-at-a-time phenomenological study where the gluonic coupling together with individual gauge boson couplings are considered. In this way, the regions excluded by experimental data for the axion-WW, axion-ZZ and axion-Zgamma couplings are determined and analyzed together with the usual photonic ones. The phenomenological results apply as well to ALPs which have anomalous couplings to both QCD and the electroweak bosons.
Highlights
Where mπ, fπ, mu, md denote the pion mass and decay constant, and the up and down quark masses, respectively
The M-dependent corrections in these couplings can be relevant for heavy axions which solve the strong CP problem as well as for gluonic axion-like particles (ALPs), as long as their mass parametrized by Eq (3.3) is sensibly larger than that for the QCD axion, M2 > m2π fπ2/ fa2
For large axion masses ma > m Z, the authors of Ref. [25] suggested that triboson final states place the strongest bounds on ALPs coupling to massive gauge bosons, though the sensitivity of this search is hindered for axions because of the large hadronic branching ratio that we take into account
Summary
The axion couplings can be encoded in a model-independent way in an effective Lagrangian. At leading order in inverse powers of the scale fPQ at which the global PQ symmetry is broken, and at energies above the electroweak (EW) scale, it reads. We will work in the basis in which the only PQ-breaking operators in the Lagrangian, δLaPQ, are the anomalous couplings of axions to gauge bosons. This choice is allowed by the reparametrization invariance of the effective axion Lagrangian (see “Appendix C”). With OG , OWand OBdenoting the anomalous axion couplings to gluons, SU (2)L and U (1)Y gauge bosons, respectively, OG. The Lagrangian in Eq (2.3) is rewritten as δLa ga0gg
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
