Question: A question about the mass of neutrinos: are neutrinos actually mass-less or is that just a simplification? I ask this because neutrinos are particles from the decay of hadrons e.g. in positron-decay (and antineutrinos in beta-decay); which were predicted because a particle was need to carry away extra momentum from the decay, which the beta particle (or positron) was not carrying. Momentum = mass x velocity, so I might be being really naive here or momentum of the neutrino/velocity = mass of neutrino.
However, in reality is this a case of E=mc squared where the mass in "momentum = mass x velocity" is actually the 'mass-energy'?
p.s. I hope this question makes sense :)
Short link to this page https://ias.im/33.2619