[en] A search for isolated electrons and muons with high transverse momentum in events with large missing transverse momentum has been conducted. The results have been found to be compatible with the Standard Model expectations. The cross section for single W production has been measured and the total cross section in electron-proton collisions at HERA has been found to be σ(ep → eWX) = 0.93_-0.23^+0.26(stat.)±0.08(syst.) pb. The measurements are based on the complete available ZEUS data sets from the HERA I and II running periods taken between 1994-2007. (orig.)