Isolated Leptons and Missing Transverse Momentum and Measurement of W Production at HERA 
(H1+ZEUS combination)

A search for events containing an isolated electron or muon and missing transverse 
momentum produced in e±p collisions is performed with the H1 and ZEUS detectors at HERA. 
The data were taken in the period 1994?2007 and correspond to an integrated luminosity 
of 0.98 fb?1. The observed event yields are in good overall agreement with the Standard 
Model prediction, which is dominated by single W production. In the e+p data, at large 
hadronic transverse momentum PXT > 25 GeV, a total of 23 events are observed compared to 
a prediction of 14.0 ± 1.9. The total single W boson production cross section is 
measured as 1.06 ± 0.16 (stat.) ± 0.07 (sys.) pb, in agreement with an SM expectation of 
1.26 ± 0.19 pb.