How would unstable neutrinos oscillate in matter? ("also" via Zoom: https://mppmu.zoom.us/j/99300254726)

by Mr Dibya Chattopadhyay (TIFR)

Thursday 30 Jun 2022, 15:00 → 16:00 Europe/Berlin

Main/0-174 - Auditorium (Main)

We find compact analytic expressions for neutrino propagation probabilities in matter, with invisible neutrino decay included in both the 2-flavor and 3-flavor formalisms. These will be directly relevant for long-baseline, reactor and atmospheric neutrino experiments. The inclusion of decay makes the effective Hamiltonian non-Hermitian. Due to a possible mismatch between the effective mass eigenstates and the decay eigenstates of neutrinos, the Hermitian and the anti-Hermitian components of this Hamiltonian need not commute. We show that in matter, these components will invariably become non-commuting. We overcome this by employing a resummation of inverse Baker-Campbell-Hausdorff (BCH) expansion, and the Cayley-Hamilton theorem. We also calculate the probabilities in the One Mass Scale Dominance (OMSD) approximation. The analytic results obtained provide physical understanding into possible effects of neutrino decay as it propagates through Earth's matter. We also show that the non-intuitive feature of decay increasing the value of the muon neutrino survival probability at its oscillation dips may be explained by our analytic expression.