Search for the standard model Higgs boson decaying to a W pair in the fully leptonic final state in pp collisions at sqrt(s) = 8 TeV

A search for the standard model Higgs boson decaying to W$^+$W$^-$ in pp collisions at $\sqrt{s} = 8$~TeV is reported. The event sample corresponds to an integrated luminosity of $5.1\pm0.2$~fb$^{-1}$, collected by the CMS detector at the LHC. The W$^+$W$^-$ candidates are selected in events with two opposite charged leptons and large missing transverse momentum. Upper limits on the Higgs boson production relative to the standard model Higgs expectation are derived. The standard model Higgs boson is excluded in the mass range 129--520~GeV at 95\% confidence level when these results are combined with the analysis performed at $\sqrt{s} = 7$~TeV. A small excess of events is observed for hypothetical low Higgs boson masses which makes the observed limits weaker than the expected ones under the null hypothesis.