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 ${\mathrm{p}\mathrm{b}}^{-1}$. 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.) $\pm 0.10$ (syst.) pb.