Question: In particle physics, a massless particle is an elementary particle whose invariant mass is zero, the discovery of this phenomenon, known as neutrino oscillation, led to which Japanese physicist, known for neutrino experiments at the Kamiokande and its successor, Super-Kamiokande, shared the 2015 Nobel prize in physics?
Sentence (from "Massless particle"): However, gluons are never observed as free particles, since they are confined within hadrons. Neutrinos were originally thought to be massless.
Relevant evidence: No