Exploring a New Model for Neutrino Propagation Using Current and Future Experiments

The existence of neutrinos has been known for nearly a century, yet the exact behavior of these particles is still unclear. Among the many questions surrounding them is the question of how exactly they propagate through space. The traditional propagation model is unitary, having real eigenvalues for the free neutrino Hamiltonian. However, recent discussion in the literature has pointed toward the possibility of a new, more detailed model - namely, one that is non-unitary. We explore the framework of one such model in which neutrinos couple to light decay states, having instead complex Hamiltonian eigenvalues. This gives rise to nine new propagation parameters in three distinct groups. We compare this model both to Tokai-to-Kamioka data and to potential future data from the Jiangmen Underground Neutrino Observatory. Specifically, we obtain constraints on the new non-unitary parameters to test the model's feasibility.