Speaker
Description
The discovery of nonzero neutrino masses naturally leads to the consideration of heavier neutrinos decaying into lighter ones. We explore the impact of two-body neutrino decays on the neutronization burst of a core-collapse supernova—the intense burst of electron neutrino emission occurring within the first 25 ms after the core bounce. In the scenario considered, the electron neutrinos are primarily produced in the more massive state and they can decay into the lightest one or their antiparticles, along with an almost massless scalar. These decays can result in the emergence of a neutronization peak in the normal ordering or the suppression of the same peak in the inverted ordering, effectively allowing one mass ordering to mimic the other. By simulating supernova-neutrino signals at the Deep Underground Neutrino Experiment (DUNE) and the Hyper-Kamiokande (HK) experiment, we evaluate their sensitivity to the neutrino lifetime. Assuming the mass ordering is known, and depending on the underlying physics driving neutrino decay, we find that DUNE can probe lifetimes of τ/m≲10^{6} s/eV for a galactic supernova within approximately 10 kpc, while HK is sensitive to lifetimes one order of magnitude larger. These constraints significantly surpass existing limits from solar-system-bound oscillation experiments. Finally, we demonstrate that by combining data from DUNE and HK, it is generally possible to distinguish between decaying Dirac and decaying Majorana neutrinos.
