Measurement of the $W^{+}W^{-}\rightarrow \ell\nu\ell\nu$ production cross-section at $\sqrt s=8$ TeV and 13 TeV and limits on anomalous triple gauge couplings with the ATLAS Detector

The production of opposite-charge $W$-boson pairs in proton-proton collisions at $\sqrt s~=~8$~TeV and $13$~TeV is measured using data corresponding respectively to 20.3~fb$^{-1}$ and 3.16~fb$^{-1}$ of integrated luminosity collected by the ATLAS detector during 2011-2012 and 2015 at the CERN Large Hadron Collider. The $WW$ pairs are reconstructed using their leptonic decays into an electron and a muon and neutrinos and no hadronic jets. An extension of the measurement is presented, which covers also the $WW+1$~jet production at 8~TeV. The cross-section measurement is performed in a fiducial phase space close to the experimental acceptance and is compared to theoretical predictions. The integrated measurement is corrected for all acceptance effects in order to obtain the total $WW$ production cross-section. Agreement is found between the measurement and the highest order QCD calculations available. Fiducial differential cross-sections are measured as a function of kinematic variables and limits on anomalous triple-gauge-boson couplings are reported.