# Dark Matter Targets for Axion-like Particle Searches

## TL;DR

This paper identifies experimental targets for axion-like particle dark matter detection across various cosmological scenarios, highlighting some experiments' potential to detect ALPs before the QCD axion and emphasizing the importance of mass origin.

## Contribution

It provides benchmark ALP dark matter targets for different cosmologies, considering temperature-dependent masses and misalignment angles, guiding future experimental searches.

## Key findings

- Some experiments can detect ALP DM targets before the QCD axion.
- Temperature-dependent ALP masses improve detection prospects.
- Certain cosmological scenarios yield lower decay constant targets.

## Abstract

Many existing and proposed experiments targeting QCD axion dark matter (DM) can also search for a broad class of axion-like particles (ALPs). We analyze the experimental sensitivities to electromagnetically-coupled ALP DM in different cosmological scenarios with the relic abundance set by the misalignment mechanism. We obtain benchmark DM targets for the standard thermal cosmology, a pre-nucleosynthesis period of early matter domination, and a period of kination. These targets are theoretically simple and assume $\mathcal{O}(1)$ misalignment angles, avoiding fine-tuning of the initial conditions. We find that some experiments will have sensitivity to these ALP DM targets before they are sensitive to the QCD axion, and others can potentially reach interesting targets below the QCD band. The ALP DM abundance also depends on the origin of the ALP mass. Temperature-dependent masses that are generated by strong dynamics (as for the QCD axion) correspond to DM candidates with smaller decay constants, resulting in even better detection prospects.