Observation and Measurement of the Higgs Boson with the $H\rightarrow WW^{(*)}\rightarrow \ell\nu\ell\nu$ Channel

We present the observation and measurement of the Higgs boson decaying to $WW^{(*)}$ in the leptonic final state using 25 fb$^{-1}$ of data collected with the ATLAS detector at the LHC in 2011 and 2012. We find an excess over the background expectation for $m_H=125.36$ GeV corresponding to 6.1 standard deviations, while the expectation is 5.8. This is the first discovery level sensitivity to the $H\rightarrow WW$ process. The ratio of the observed to expected number of signal-like events is $1.09^{+0.23}_{-0.21}$, the most precise such single-channel measurement with ATLAS. These are the final Run I ATLAS $H\rightarrow WW^{(*)}\rightarrow \ell\nu\ell\nu$ results.