Neutrino oscillations as two-slit experiments in momentum space

The passage of a neutrino from source to detector is described as a multipath experiment where knowing the path destroys coherence. The concept of partial coherence and partial dephasing is developed in a toy model for recent mesoscopic `which-pathʹ experiments and shown to require considering the beam and the detector as a correlated quantum system. The application to Bragg scattering by X-rays gives the Debye–Waller factor. Neutrino amplitudes with the same energy and different masses are shown to be detected coherently and can produce oscillations at a detector localized for long times in space. Amplitudes with different energies are incoherent. Quantum mechanics alone shows the existence of a neutrino mass difference. to be required to explain the observed Super-Kamiokande data.