Stellar cooling bounds on new light particles: including plasma effects
Ed Hardy (ICTP Trieste)

Strong constraints on the coupling of new light particles to the Standard Model (SM) arise from their production in the hot cores of stars, and the effects of this on stellar cooling. However, the large electron density in stellar cores significantly modifies the in-medium propagation of SM states. I will show that, for new light particles which have an effective in-medium mixing with SM states, this can result in parametrically different production rates to those obtained from a naive calculation.
Taking these previously-neglected contributions into account, I will give updated estimates for the stellar cooling bounds on a number of light new particle candidates. In particular, the bounds on light (m < keV) scalars coupling to electrons (nucleons) are strengthened by up to 5 (up to 3) orders of magnitude in the coupling squared. Supernova cooling bounds on dark photons are also significantly modified.