The frontier of feebly interacting particles: from dark matter to the muon (g-2) - Lecture II

New light but Feebly Interacting Particles (FIPs) represent an exciting and well-motivated class of new physics particles. FIPs are loosely defined as (1) singlets under the Standard Model (SM) gauge groups; (2) lighter than the electroweak scale and (3) not yet excluded or discovered. Many well-grounded new physics candidates fit this definition, with extremely bright experimental prospects for FIPs in the MeV and GeV mass range. In these lectures, we will present the theoretical foundations of this family of new physics particles and introduce some of its most searched-for members. The links between FIPs and the dark matter problem will be explored, along with their potential in explaining various low-energy experimental anomalies, including the measured anomalous magnetic moment.