New Supernova Constraints on Neutrinophilic Dark Sector - Vector Mediators

Supernova cooling has long been used to constrain physics beyond the Standard Model, typically involving new mediators or dark matter (DM) particles that couple to nucleons or electrons. In this work, we show that the large density of neutrinos inside the neutrinosphere of supernovae also makes them powerful laboratories to study nonstandard neutrino interactions with a {\it neutrinophilic} dark sector, i.e.~DM and mediator particles interacting primarily with neutrinos. In this case, we find that the existing constraints are rather weak, and for a wide range of currently unconstrained parameter space, neutrino annihilation within a supernova could copiously produce such neutrinophilic DM at a large enough rate to cause noticeable anomalous cooling. From the non-observation of such anomalous cooling in SN1987A, we thus set new constraints on neutrino-DM interactions, which provide up to five orders of magnitude improvement in the effective coupling over the existing constraints for DM masses below ${\cal O}$(100 MeV).