Dark matter is believed to constitute most of the matter in our Universe, yet its particle nature remains elusive. Traditionally, experimental searches have concentrated on dark matter candidates with masses near that of the Higgs boson. However, lighter dark matter particles, particularly those residing in a hidden dark sector, are also theoretically well-motivated and emerge naturally in many extensions of the Standard Model. Moreover, dark sectors offer potential solutions to longstanding problems in particle physics and cosmology, such as the strong CP problem, which axions or axion-like particles can help address.
In this colloquium, I will present recent theoretical and phenomenological advances in the study of light dark sectors. I will then discuss new experimental avenues, focusing on high-intensity accelerator experiments—specifically PIONEER and DarkQuest—that are uniquely positioned to explore viable light dark sector models in the near future.