Search for events with an isolated lepton and missing transverse momentum and a measurement of W production at HERA

A search for events with an isolated high-energy lepton and large missing transverse momentum has been performed with the ZEUS detector at HERA using a total integrated luminosity of 504 pb−1. The results agree well with Standard Model predictions. The cross section for production of single W   bosons in electron–proton collisions with unpolarised electrons is measured to be 0.89−0.22+0.25(stat.)±0.10(syst.)pb.