Measurements of the properties of the Higgs-like boson in the $WW^{(\ast)} \to \ell \nu \ell \nu$ decay channel with the ATLAS detector using 25 fb$^{-1}$ of proton-proton collision data

Evidence for the Higgs-like boson in the $H \to WW^{(\ast)} \to \ell\nu\ell\nu$ channel is presented using the complete 2012 and 2011 data samples collected with the ATLAS detector at the LHC. The samples correspond, respectively, 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. The analysis focuses on such a boson in the Standard Model with a mass of $m_{\rm H}\,{=}\,125$ GeV, where an excess over the expected number of background events is observed. The significance of the excess is 3.8 standard deviations; the expected value is 3.7. The ratio of the observed and expected numbers of events is consistent with unity, $\mu\,{=}\, 1.01 \pm 0.31$. The case where the signal is accompanied by two or more jets is optimised for the vector boson fusion production process, and the significance of the excess is 2.5 standard deviations; the expected value is 1.6. The product of the Higgs boson cross section at 8 TeV and the branching ratio to $WW^{(\ast)}$ is measured to be $6.0 \pm 1.5$ pb; the expected value is $4.8 \pm 0.7$ pb.