Pion beta decay (${\pi }^{+}\to {\pi }^0{e}^{+}{\nu }_e$)

Pion beta decay changes a charged pion into a neutral pion and a lepton pair through the weak charged current. The small charged-neutral pion mass gap severely restricts phase space, giving an approximately fifth-power dependence on that gap. It does not have the charged-lepton mass suppression of direct leptonic pion decay.