Speaker
Description
Neutrino self-interactions beyond the Standard Model are well motivated by nonzero neutrino masses. We explore a scenario in which the lightest neutrino species remains relativistic today, leading to a broadened “widened” resonance in neutrino scattering that enhances sensitivity to new physics. This effect enables probes of neutrino self-interactions across a wide mediator mass range: (1) Hyper-Kamiokande observations of the diffuse supernova neutrino background can reach sub-keV mediators with couplings as small as g∼1e-8 (2501.07624 PRL); (2) ultra-high-energy neutrino experiments such as GRAND can test MeV–GeV mediators down to g~1e-3 (2512.00165). This unified framework opens new opportunities to probe neutrino properties and their connections to the dark sector across multiple energy scales.