New bounds on light bosons - from stars to colliders

Abstract: Many models of beyond-Standard-Model physics include new light, weakly-coupled particles, and some of the best constraints on such particles come from stellar energy loss bounds. I will discuss how, for new light particles which gain an effective in-medium mixing with the photon (or other SM particle), plasma effects can result in parametrically different thermal production rates to those obtained from a naive calculation. This can result in orders-of-magnitude improvements in sensitivity to the couplings of light scalars, and qualitative changes to the sensitivity for light vectors. 

Collider experiments can also provide strong bounds, and future discovery potential, for light weakly-coupled states. In the case of new light vectors, there are generically (energy/vector mass)^2 enhanced production processes for the longitudinal mode, which allow high-energy experiments to act as powerful probes of light vectors. I’ll discuss such experimental probes, and show how they apply even in cases where the vector couples to an anomalous but tree-level conserved current such as baryon number.