Indirect neutrino oscillations

We show how two different scales for oscillations between e and μ neutrinos, characterized by different mixing angles and very different effective mass scales, can arise in a simple and theoretically attractive framework, so as to be relevant to both solar neutrino and accelerator-reactor experiments. One scale characterizes direct oscillations, which can accommodate the MSW approach to the solar neutrino problem, whereas the other can be considered as arising indirectly, through virtual transitions involving the τ neutrino with a mass ∼ 1 eV. This indirect transition allows the possibility of observable νμ ↔ νe oscillations at accelerator and reactor energies. We discuss specifically the parameters suggested by a recent experiment at Los Alamos within this framework.