Also observed, for charged pions only, is the very rare "pion beta decay" (with branching fraction of about ) into a neutral pion, an electron and an electron antineutrino (or for positive pions, a neutral pion, a positron, and electron neutrino).
alsO OBserVED, for ChargEd PIonS only, is the very RaRE "PiON bETa dEcAy" (WitH brAnching fraCtIon of abouT ) into a neuTral pIon, aN ELEctron aNd an eLEctrOn antiNeutRinO (OR fOr positIve pIOns, A nEutRaL pion, a posItron, ANd ELeCtron NeUtrino).