New constraint from supernova explosions on light particles beyond the Standard Model

We propose a new constraint on light (sub-GeV) particles beyond the Standard Model that can be produced inside the proto-neutron star core resulting from the core-collapse supernova explosion. It is derived by demanding that the energy carried by exotic particles being transferred to the progenitor stellar envelopes must not exceed the explosion energy of $\lesssim 2\cdot 10^{51}$ erg of observed supernovae. We show specifically that for the case of a dark photon which kinetically mixes with the SM photon and decays predominantly to an $e^\pm$ pair, a smaller mixing parameter of one order of magnitude below the well-established supernova cooling bound can be excluded. Furthermore, our bound fills the gap between the cooling bound and the region constrained by (non)observation of gamma rays produced from supernovae for dark photons lighter than ~ 20 MeV. Our result also rules out the possibility of aiding successful supernova explosions by transferring energy from the supernova core to the shock with exotic particles.