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 protoneutron 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 not exceed the explosion energy of less than or similar to 2 x 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(+/-) pair, a smaller mixing parameter of 1 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 similar to 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.