K + → μ + ν μ ν ν ¯ $$ {\mathrm{K}}^{+}\to {\mu}^{+}{\nu}_{\mu}\nu \overline{\nu} $$ and K + → e + ν e ν ν ¯ $$ {\mathrm{K}}^{+}\to {\mathrm{e}}^{+}{\nu}_{\mathrm{e}}\nu \overline{\nu} $$ decays within the Chiral Perturbation Theory
D. Gorbunov (Theoretical Physics Division, Institute for Nuclear Research of the Russian Academy of Sciences, 60th October anniversary prospect, 7a, Moscow, 117312, Russia, Department of Problems of Physics and Energetics Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Moscow Region, 141700, Russia); A. Mitrofanov (Theoretical Physics Division, Institute for Nuclear Research of the Russian Academy of Sciences, 60th October anniversary prospect, 7a, Moscow, 117312, Russia, Department of Problems of Physics and Energetics Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Moscow Region, 141700, Russia)
Decays K + → μ + ν μ ν ν ¯ $$ {K}^{+}\to {\mu}^{+}{\nu}_{\mu}\nu \overline{\nu} $$ and K + → e + ν e ν ν ¯ $$ {K}^{+}\to {e}^{+}{\nu}_e\nu \overline{\nu} $$ are examined to the leading order in momenta in the framework of Chiral Perturbation Theory. Predictions of the Standard Model for the muon and electron differential energy spectra and branching ratios of K μ3ν and K e3ν are presented.