Phenomenology of the axion-portal and the vector-portal and their combination

Abstract

We discuss various phenomenological aspects of axion- and vector-portal and their combination. We give a brief review of what the dark photon and the axion-like particles (ALPs) are, especially focusing on their key features in phenomenology. For the vector-portal physics, we study the interaction mediated by a light gauge boson appearing from a minimal gauge extension of the Standard Model with the $U(1)_{B-L-xY}$ symmetry. We perform a thorough study including the axial coupling that provides very different phenomenology in its production from a heavy particle decay and the parity violation tests. For axion-portal physics, we discuss the radiatively induced flavor-changing ALP couplings in the context of manifestly gauge invariant effective lagrangian. We also examine their implications with a discussion of the possible UV completion providing the origin of the relevant bare ALP couplings. After that, we introduce a new portal, called the “dark axion” portal, that connects the dark photon and the ALP physics. This new portal can be realized not only by a product of two portals, but also by an anomalous triangle loop with an exotic fermion charged under the visible and hidden gauge symmetry and the global Peccei-Quinn symmtery. Although laboratory experiments might be pessimistic to catch the signals of ALPs or dark photons via the dark axion portal due to their lightness and feeble interactions to the visible sector, astrophysical and/or cosmological implications may reveal the truth about dark axion portal with its own phenomenological consequences. For the start, we investigate the photon-ALP-dark photon oscillations in the presence of the background dark photon field and the usual external magnetic field and examine the gamma-ray spectral modulations of point-like sources. We also discuss new mechanisms to produce the dark photon in the early universe with the help of the axion using the dark axion portal. We will see that the dark photon can be a dark matter candidate if its lifetime is long enough.