Measurement of WW production rate

This document reports on a measurement of $\ensuremath{\mathrm{W}}^{+}\ensuremath{\mathrm{W}}^{-}$ production in pp collisions at $\sqrt{s} = $ 7~TeV. The data were collected at the LHC with the CMS detector, and correspond to an integrated luminosity of $4.92~\ifb$. The $\ensuremath{\mathrm{W}}^{+}\ensuremath{\mathrm{W}}^{-}$ candidates are selected in events with two charged leptons (electrons or muons) and large missing transverse energy. The $\ensuremath{\mathrm{W}}^{+}\ensuremath{\mathrm{W}}^{-}$ cross section is measured to be $52.4 \pm 2.0~(\rm{stat.})~\pm 4.5~(\rm{syst.})~\pm 1.2~(lumi.)~\mathrm{pb}$.