A study of the Higgs channel pp → H → WW → ℓνℓν for a mass between 150 and 180 GeV is presented. Signal and background systematics are invest igated in detail, including the implementation of most up-to-date higher order QCD correct ions for signal and background. For the first time full detector simulations are performed in this channel. A data driven approach to determine the size of the backgrounds is used. A S tandard Model Higgs boson can be discovered in the H → WW → ℓνℓν channel with an integrated luminosity of less than 1 fb − 1 if its mass is around 165 GeV. If it has a mass between 150 and 18 0 GeV, a 5 σ signal can be seen with a luminosity of about 10 fb − 1 . Assuming that the LHC experiments will discover a Higgs-like signal in this channel, different experimental observables have been analysed in order to establish how and how well the Higgs mass can be measured in this mass range. Combining the hypothetical cross section measureme nt with the lepton p T spectra and the estimated systematic uncertainties of 10 to 15%, ass ociated with this signature, we find that the mass of a Standard-Model-Higgs-like signal in t he mass range between 150 and 180 GeV can be measured with an accuracy of 2 to 2.5 GeV. In c ase that no further improvements in the systematics for this channel can be achi eved, our analysis shows also that such a mass measurement will be dominated by systematic uncertainties once integrated luminosities of about 10-20 fb − 1 can be analysed
