The link between oscillation and massIn the final step, we just rewrite the last equation from the previous page. We know from many earlier experiments that the neutrino mass, if any, must be much smaller than the kinetic energy of the neutrinos. This allows us to rewrite the difference in energies as a difference in masses squared, and arrive at the final result that, if the probability for a muon neutrino changing into a tau neutrino is nonzero, the differences in masses squared must be nonzero because sin(0) = 0.
