Probing Dark-ALP Portals at Future $e^{+}{e}^{-}$ Colliders

Abstract

We study portal interactions connecting visible and dark sectors, and involving local interactions of a photon, a dark photon and a axion-like particle (ALP) at future $e^{+}{e}^{-}$ colliders. These interactions, mediated by higher-dimensional effective operators, may arise at one-loop by kinetic mixing between dark and ordinary photons, or, for massless dark photons, by direct short-distance contributions. We explore these portal interactions for a heavy ALP with masses between about 10 GeV and 230 GeV by investigating the sensitivity of the production $e^{+}{e}^{-}\to \gamma \gamma \bar{\gamma }$ to the effective couplings, where the dark photon $\bar{\gamma }$ gives rise to missing momentum in the final state. We will show how an appropriate choice of missing-energy and missing-mass cuts can optimize the signal to standard-model background ratio. Exclusion regions for the effective photon-dark-photon-ALP couplings versus the ALP mass are worked out for a few representative values of the collision energy and integrated luminosity, as presently envisaged by future $e^{+}{e}^{-}$ projects.

14 pages, 13 figures, 4 tables; LEP bound included, references added