PDF《CERN-PH-EP-2012-019》

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600 GeV mass range using data corresponding to an integrated luminosity of 4.8 fb?1 [10]. The main ir- reducible ZZ(?) background is estimated using Monte Carlo simulation. The reducible Z+jets background, which has an impact mostly for low four-lepton invari- ant masses, is estimated from control regions in the data. The top-quark background normalisation is val- idated in a control sample of events with an opposite sign electron-muon pair with an invariant mass consis- tent with that of the Z boson and two leptons of the same ?avour. The events are categorised according to the lep- ton ?avour combinations. The mass resolutions are ap- proximately 1.5% in the four-muon channel and 2% in the four-electron channel for mH?120 GeV. The four- lepton invariant mass is used as a discriminating vari- able. Its distribution for events selected after all cuts is displayed in Fig. 1(b) for the low mass range and Fig. 1(c) for the full mass range. The H → WW(?) → ?+ ν?′? ν search is performed as an event counting analysis for mH hypotheses between

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60 -1 Ldt = 2.05 fb ∫ ATLAS Data =130 GeV, 1xSM H m Total background ν l ν l → (*) WW → H 0+1 jet (c) (d) Figure 1: Distributions of the reconstructed invariant or transverse mass for the selected candidate events and for the total background and signal (mH=130 GeV) expected in the H → γγ (a), the H → ZZ(in the low mass region (b) and the entire mass range (c), and the H → WW(?) → ?+ ν?′? ν (d) channels. from the data using control regions based on the dilep- ton invariant mass m??. The analysis is separated into 0-jet and 1-jet categories as well as according to lep- ton ?avour. In the 1-jet category, a b-jet veto is applied to reject events from top-quark production. The rela- tive fractions of the background contributions expected in the signal and control regions are taken from Monte Carlo simulation. The transverse mass distribution of events for both jet categories is displayed in Fig. 1(d). The H → WW → ?νqq′ analysis covers mH hypothe- ses in the

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600 GeV range and is carried out using data corresponding to an integrated luminosity of 1.04 fb?1 [12]. This channel is also separated accord- ing to lepton ?avour and into 0-jet and 1-jet categories, where the number of jets refers to those in addition to the jets selected as originating from the W-boson de- cay. Events with at least one b-tagged jet are rejected to reduce backgrounds from top-quark production. The ?νqq′ mass is reconstructed using a constraint to the ?ν system to W-boson mass. It is used as a discriminating variable and its distribution is illustrated in Fig. 2(a). The search in the H → ZZ → ?+ ?? νν channel is per- formed in the