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

## TL;DR

This paper investigates how future electron-positron colliders can detect interactions between visible particles and dark sector particles involving photons, dark photons, and ALPs, by analyzing specific production processes and optimizing detection strategies.

## Contribution

It introduces a novel analysis of portal interactions involving ALPs and dark photons at future colliders, focusing on sensitivity and exclusion limits for effective couplings.

## Key findings

- Identifies optimal missing-energy cuts to distinguish signal from background.
- Provides exclusion regions for couplings based on collider energy and luminosity.
- Demonstrates potential to probe dark sector interactions at upcoming 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.