Searches for heavy neutrinos in the decays of positively charged kaons

According to predictions of the νMSM model, a heavy neutrino may exist in the mass range below 1 GeV. Searches for rare kaon decays make it possible to study the heavy-neutrino-mass range M _π < m _{ν H} < M _K . A preliminary analysis of data from the E949 experiment performed at the Brookhaven National Laboratory (BNL, USA) is performed in the present study. Basic background processes are studied, and it is shown that a sensitivity at a level of 4 × 10⁻⁸ to the K ⁺ → μ⁺ ν _H branching ratio can be reached for the mass value of m _{ν H} = 250 MeV.