Discrete Abelian gauge symmetries and axions

Gabriele Honecker,Wieland Staessens

doi:10.1088/1742-6596/631/1/012080

Abstract

We combine two popular extensions of beyond the Standard Model physics within the framework of intersecting D6-brane models: discrete ℤn symmetries and Peccei-Quinn axions. The underlying natural connection between both extensions is formed by the presence of massive U(1) gauge symmetries in D-brane model building. Global intersecting D6-brane models on toroidal orbifolds of the type T6/ℤ2N and T6/ℤ2 × ℤ2M with discrete torsion offer excellent playgrounds for realizing these extensions. A generation-dependent ℤ2 symmetry is identified in a global Pati-Salam model, while global left-right symmetric models give rise to supersymmetric realizations of the DFSZ axion model. In one class of the latter models, the axion as well as Standard Model particles carry a non-trivial ℤ3 charge.

Highlights

Extensions of the Standard Model are characterised by the inclusion of new particles to resolve open questions arising in particle physics and cosmology
The perturbative behaviour at low energy of such a massive U (1) corresponds to a global continuous symmetry, which is expected to be broken by non-perturbative effects such as instantons
We briefly reviewed the conditions on the existence of discrete Zn symmetries for global intersecting D6-brane models on toroidal orbifolds and Calabi-Yau manifolds, for which the unimodular basis of three-cycles is not aligned with the symmetry planes of the anti-holomorphic orientifold involution ΩR

Summary

Introduction

Extensions of the Standard Model are characterised by the inclusion of new particles to resolve open questions arising in particle physics and cosmology. The massive Abelian vectors lead to global U (1) symmetries in perturbation theory, which might be broken explicitly by vacuum expectation values of light charged open string states. This is exactly the stringy generalization of a field theoretical Peccei-Quinn symmetry. . .) with underlining denoting all possible permutations of entries, whose solution is ZN ⊂ U (N ) Even though this ZN symmetry does not correspond to the center of SU (N ), the charge assignment of any open string in the fundamental (N) or antisymmetric (Anti) representation of SU (N ) × U (1) ≃ U (N ) or the respective conjugates (N)−1=N−1 mod N and (Anti)−2=N−2 mod N is so constraining that the ZN selection rules on couplings do not provide any constraints beyond those imposed by the non-Abelian SU (N ) representations.

Local versus global D-brane models

Discrete symmetries in models with axion candidates

Open string axions and axion mixing

Conclusions