A search for the $K^{+}\to {\mu }^{-}\nu e^{+}{e}^{+}$ decay

NA62 collaboration

A search for the $K^{+}\to {\mu }^{-}\nu e^{+}{e}^{+}$ decay, forbidden within the Standard Model by either lepton number or lepton flavour conservation depending on the flavour of the emitted neutri…