Rare kaon decays due to the loop-induced standard model operator s${\mathrm{¯}}_{\mathit{L}}$${\gamma }_{\mathrm{\mu }}$${\mathit{d}}_{\mathit{L}}$ν${\mathrm{¯}}_{\mathit{L}}$${\gamma }^{\mathrm{\mu }}$${\nu }_{\mathit{L}}$ are examined. Isospin-violating mass effects and electroweak radiative corrections are shown to reduce B(${\mathit{K}}^{+}$→${\mathrm{\pi }}^{+}$νν¯) and B(${\mathit{K}}_{\mathit{L}}$→${\mathrm{\pi }}^0$νν¯) relative to B(${\mathit{K}}^{+}$→${\mathrm{\pi }}^0$${\mathit{e}}^{+}$${\nu }_{\mathit{e}}$) by 10% and 5.6%, respectively. Predicted branching ratios for (${\mathit{K}}_{\mathit{L}}$→νν¯γ) and (${\mathit{K}}_{\mathit{L}}$→νν¯) (if neutrinos have mass) are given. The sensitivity of ‘‘missing energy’’ rare K decays to new interactions or the emission of light weakly interacting neutral particles, other than neutrinos, is also briefly discussed. © 1995 The American Physical Society.

• Received 30 August 1995

DOI:https://doi.org/10.1103/PhysRevD.53.R1