image: Left Panel: When neutrinos scatter with themselves via standard model interactions the collapsing core of the massive star is relatively cold, and the neutrinos are mostly all electron flavor. In this scenario we may get a supernova explosion leaving, usually, a neutron star remnant. Right Panel: If neutrinos have "secret" interactions with themselves, then electron neutrinos can be converted to all flavors. This leads to rapid heating, the “melting” of nuclei, and the rapid conversion of most protons to neutrons. We might get a black hole instead of a neutron star remnant. It is not yet clear if we get a supernova explosion.
Credit: George Fuller lab / UC San Diego
Neutrinos are cosmic tricksters, paradoxically hardly there but lethal to stars significantly more massive than the sun. These elementary particles come in three known “flavors”: electron, muon and tau. Whatever the flavor, neutrinos are notoriously slippery, and much about their properties remains mysterious. It is almost impossible to collide neutrinos with each other in the lab, so it is not known if neutrinos interact with each other according to the standard model of particle physics, or if there are much-speculated “secret” interactions only among neutrinos.
Now a team of researchers from the Network for Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS), including several from UC San Diego, have shown, through theoretical calculations, how collapsing massive stars can act as a "neutrino collider.” Neutrinos steal thermal energy from these stars, forcing them to contract and causing their electrons to move near light speed. This drives the stars to instability and collapse
Eventually the collapsing star’s density becomes so high that the neutrinos are trapped and collide with each other. With purely standard model interactions, the neutrinos will be mostly electron flavor, the matter will be relatively “cold,” and the collapse will likely leave a neutron star remnant. However, secret interactions that change neutrino flavor radically alter this scenario, producing neutrinos of all flavors and leading to a mostly neutron “hot” core that may lead to a black hole remnant.
Fermi National Accelerator Lab’s upcoming Deep Underground Neutrino Experiment (DUNE) might be able to test these ideas, as might future observations of the neutrinos or gravitational waves from collapsing stars.
The study, published June 18, 2025 in Physical Review Letters, was led by UC San Diego researchers Anna M. Suliga, Julien Froustey, Lukáš Gráf, Kyle Kehrer and George Fuller, as well as collaborators from other institutions. Their research was funded, in part, by the National Science Foundation (PHY-2209578 and PHY-2020275), the Department of Energy (DE-AC02-07CHI11359), and the Heising-Simons Foundation (2017-228).
Journal
Physical Review Letters
Method of Research
Computational simulation/modeling
Article Title
Nonconservation of Lepton Numbers in the Neutrino Sector Could Change the Prospects for Core Collapse Supernova Explosions
Article Publication Date
18-Jun-2025