Speaker: Stefania Gori (UCSC)-Title: New meson probes of axion-like-particles

Meson factories are at the cutting edge of the intensity frontier, with an unprecedented number of pions, Kaons, and B mesons that will be produced in the coming years. In addition to precise measurements of Standard Model processes, these experiments have a unique opportunity to search for dark sector particles in the sub-GeV mass range. In this talk, we will first give an overview of new opportunities to search for axion-like particles (ALPs) in light meson decays. Such ALPs can be motivated by a solution to the hierarchy problem, the strong CP problem, the flavor puzzle, and combinations of these with DM physics.  Second, we revisit the theory and constraints on ALPs interacting with leptons, pointing out the relevance of charged current meson and W decays to ALPs. This is particularly prominent in models where the ALP couples in an isospin-violating way. Finally, we highlight the role of the future PIONEER experiment in probing these new charged current pion decays to ALPs.