Shedding light on dark matter spikes through refractive neutrino masses

The origin of neutrino mass remains an open question in particle physics. One intriguing possibility is that neutrinos are massless in vacuum but acquire an effective refractive mass through interactions with ultralight dark matter during propagation. We investigate the capability of the upcoming Deep Underground Neutrino Experiment (DUNE) to probe such refractive masses using the time-of-flight delays of neutrinos from a galactic core-collapse supernova. Our analysis shows that DUNE can set competitive bounds on the refractive neutrino mass, with sensitivity significantly enhanced if neutrinos traverse a dark matter density spike near the Galactic Center. In particular, we quantify how the presence of a spike modifies the projected limits, demonstrating that supernova neutrino observations at DUNE provide a powerful and novel avenue to test both the nature of neutrino masses and the distribution of dark matter in the innermost regions of the Milky Way.