when an electron neutrino is produced in the sun, it have the total energy of E. the total energy E have the relation with mass and momentum as E2=p2+m2. during the journey of its propagation from sun to earth, the electron neutrino change their flavor to muon neutrino which have mass m', momentum p', and energy E'. E2-p2=m2 (initial) E'2-p'2=m'2 where m'>m (final) then the four vector momentum is not conserved ie m'>m. if we say the energy and momentum is conserved, E=E', p=p', then m'=m. but in reality we know than m'>m I am confusing...can anybody helps?