Measurement of the Higgs boson properties in the $WW^{(*)} \rightarrow \ell \nu \ell \nu$ decay mode with the ATLAS detector at the LHC

This article describes the measurements of the Higgs boson properties in the $H \rightarrow WW^{(\ast)} \rightarrow \ell \nu \ell \nu$ ($\ell = e, \mu$) decay mode using the ATLAS detector at the CERN Large Hadron Collider. The results are obtained using the proton-proton collisions dataset which corresponds to an integrated luminosity of 20.7 fb$^{-1}$ at a centre of mass energy of 8 TeV and 4.6 fb$^{-1}$ at 7 TeV. An excess over the expected number of background events is observed in the data. The significance of the excess for the Higgs boson with a mass of 125 GeV is estimated to be 3.8 standard deviations, while the expected value is 3.7. The signal strength $\mu$, defined as a ratio of the cross-section for the observed signal to the cross section predicted for a Standard Model Higgs boson with a mass of 125 GeV, is measured to be $\mu = 1.01 \pm 0.31$. The results obtained by including the $H \rightarrow WW^{(\ast)} \rightarrow \ell \nu \ell \nu$ channel where the Higgs boson is produced in association with a $W$ or a $Z$ boson which decay leptonically are also reported. Finally, results of the searches for resonances up to 1 TeV are briefly summarised. An additional signal with the Standard Model like production cross-section and couplings is excluded in the range 260 $< m_{H} <$~642 GeV.