Dark gauge boson emission from supernova pions

The hot, neutron-rich, and dense circumstance in core-collapse supernovae provides a source of negatively charged pions that may make up a significant portion of the matter. These abundant thermal pions can play a role to populate light and hidden hypothetical particles. We discuss the dark gauge boson production via reactions involving supernova pions, the rate of which is determined by the isovector nucleon coupling. We take into account the two toy models, the dark photon and the gauged $B-L$ models, that carry the typical distinct isovector nucleon coupling structure in the medium. Pion-induced dark gauge bosons leave an imprint on several observational consequences associated with supernova. Their sizable emissivity and characteristic hard spectral distribution result in the stringent constraints on the dark gauge boson models, in particular at masses above the two electron mass.