In the Standard Model of particle physics, neutrinos only interact through the weak nuclear force. Several proposed extensions to the Standard Model introduce additional ways that neutrinos could interact with each other (but not with different types of particles), and these are known as secret interactions. Shalgar et al. calculated how any secret interactions would affect core-collapse supernovae, in which an explosion is driven by a vast flux of neutrinos flowing outward from a dying star’s core. If there were secret interactions, then neutrinos would become trapped in the core and no supernova would occur. The authors used this to set upper limits on neutrino physics beyond the Standard Model.
Phys. Rev. D 103, 123008 (2021).