Measurement of the Jet Momentum Resolution and Search for a light Standard Model Higgs Boson in the H(bb)W(lv) Channel with the CMS Detector at the LHC

The Higgs boson is the last particle predicted by the Standard Model which remains undetected. Its potential discovery was a main objective of the construction of the Large Hadron Collider (LHC) at CERN. Its exclusion would necessitate the existence of new physics beyond the Standard Model. A search for the Higgs boson decaying into two bottom quarks in association with the production of a leptonically decaying W boson is presented based on pp collision data recorded with the CMS experiment in 2011, corresponding to an integrated luminosity of L = 4.65 fb−1. Events are selected requiring the presence of an isolated charged lepton (electron or muon), missing transverse energy and two b-jets, which are clustered with the anti-kT jet algorithm at first. The search is performed in a boosted event topology, where both the W boson and the Higgs boson candidates have high momenta and move back-to-back in the transverse detector plane. Artificial Neural Networks are employed to discriminate signal and background events. No significant excess of signal events is observed and upper CLs 95% confidence level exclusion limits are calculated relative to the Standard Model prediction for different Higgs boson trial masses m(H): m(H) [GeV/c2] 110 115 120 125 130 135 CLs expected 4.66 5.05 6.13 7.22 8.94 10.9 CLs observed 4.45 6.33 6.65 7.49 8.95 11.6 The analysis is performed twice, based on different reconstruction techniques of the H ! b¯b decay. First, standard anti-kT jets are used, then a fat-, sub- and filterjet clustering algorithm specifically designed for the reconstruction of boosted objects is applied. The latter approach shows possible improvements in the expected search sensitivity of 2 − 10% and is considered for the 2012 data-taking period. The precise knowledge of the jet pT resolution is important for analyses with jets in the final state, and it is needed for the understanding of the mass resolution of the jet-based Higgs boson candidates. The first measurement of the jet pT resolution at CMS applying the data-driven dijet asymmetry method to the 2010 pp dataset, corresponding to an integrated luminosity of L = 35.9 pb−1, is presented. The resolution in data is found to be systematically poorer compared to simulation. A resolution scaling method is applied to events from simulation to account for this discrepancy. The jet pT resolutions are key ingredients to the measurements of the inclusive jet and b-jet cross sections, which are summarized.