IV.P125 — Beta-decay Q-value

The beta-decay Q-value Q_beta = (delta_A - m_e)c^2 = (1.293 - 0.511) MeV ~ 0.782 MeV, with both delta_A and m_e determined by iota_tau through the mass ratio chain; the experimental value Q_beta = 0.782333(4) MeV confirms sub-percent agreement.