I understand that a beta plus decay emits positron and beta minus decay emits electron. For the calculation of kinetic energy of the particle released, you take into account the mass of electron for beta plus, but why is it that you DON'T take into account the mass of electron for beta minus? I kind of heard that the mass of electron cancels out for beta minus decay. I do not see how that happens. If you could show me how the mass of electron "cancels out" when calculating the kinetic energy released for beta minus decay, I would feel extremely grateful. Thank you for taking your time to read my question.