Natural Science Forum / Physics / Particle Physics / October 2004

No.  First, since neutrinos have mass, their speed depends on their
energy.  Second, the "mass states" are not the same as the "flavor
states", but are mixtures of each other.  So the speed also depends on
which particular mass state ends up being "picked out" by the interaction
that detects the neutrino.

However, the masses (and the differences between them) are very small, and
nobody has yet seen any direct experimental evidence of neutrinos
traveling at a speed less than c (let alone at different speeds for the
different mass states), as far as I know.  In fact, I'll be rather
surprised if anybody ever *does* detect those different speeds. they're so
close together and detecting neutrinos is such a tricky business anyway.

For practical calculations, everybody continues to set the speed of a
neutrino to c, as far as I know.

who says photons have no mass?...