Measurement of the $W^+W^-$ production cross section in proton-proton collisions at $\sqrt{s} =8$ TeV with the ATLAS detector

This note reports a measurement of the $W^+W^-$ production cross section in $pp$ collisions at $\sqrt s =\ $8 TeV. The $W^+W^-$ leptonic decay channels are analysed using data corresponding to $\cal{L} = $ 20.3 fb$^{-1}$ of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The measurements of the fiducial and total production cross section are reported and compared to theoretical predictions. The measured WW production cross section in the total phase space is $71.4 ^{+1.2}_{-1.2} $ (stat) $^{+5.0}_{-4.4}$ (syst) $^{+2.2}_{-2.1}$ (lumi)~pb.