RevModPhys.84.1477】Tests of the standard electroweak model at the energy frontier

And therefore provides a control sample used to

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Unformatted text preview: .7 70.9 11.2 8.35 6.24 4.77 33.4 24.8 18.5 14.2 of a significant signal resulting from the fits determines the mass limit (indicates discovery). The low mass Higgs searches using the ZH ! bb channel and final states involving one or two  lepton decays follow different strategies. The ZH ! bb channel has significant background from multijet QCD processes without real vector boson decay2 in which mismeasurement of jets results in significant ET . In this channel, an additional step 6 (described later in this section) is added to improve an understanding of this background. The search using final states that involve either one or two  leptons does not make use of b-jet identification since the  leptons can arise either from Higgsboson decay or from W or Z decay. The latest low mass Higgs searches from CDF and D0 are described in Sec. V.B.5. The most recent combination of low mass results, which includes some preliminary results not presented here, is described in Secs. V.C. For mH * 135 GeV=c2 (the ‘‘high mass Higgs’’ region), the dominant Higgs decay is to W boson pairs with the next largest contribution being H ! ZZðÃÞ . Aside from a region around mH ¼ 150 GeV=c2 where BRðH ! ZZðÃÞ Þ peaks to $10%, the H ! WW ðÃÞ decay where one of the final-state W bosons is off shell for MH less than twice the W mass completely dominates over the sensitive region of the Tevatron. The Higgs production cross section and branching fractions for several Higgs masses in the high mass region are shown in Table XXIX. The standard model Higgs-boson branching fraction to WW à varies from 7.5% at 115 GeV=c2 to 73.5% at 200 GeV=c2 with a maximum of 96.5% at % 170 GeV=c2 (Djouadi, 2008). For MH $ 170 GeV=c2 , the standard model Higgs boson decays almost exclusively to two on-shell W bosons, making this a region where the Tevatron has the best chance at a discovery or an exclusion. At the Tevatron, the most sensitive Higgs search channel over the range 135 & mH & 200 GeV=c2 is gg ! H ! WW ðÃÞ ! ‘‘, where the two charged leptons in the final state are of opposite charge (Han, Turcot, and Zhang, 1999; Han and Zhang, 1999). The ‘‘ final state represents 6.0% of all WW à decays, where ‘ is either an electron or a muon, including those from  leptons produced in the W decays. Over the last few years, the experimental search for a high mass Higgs in decay to WW at the Tevatron has evolved substantially to include powerful multivariate techniques and additional H ! WW ðÃÞ processes such as VBF H ! WW ðÃÞ and VH ð! WW ðÃÞ Þ. The latest high mass Higgs searches in the H ! WW ðÃÞ channel from CDF and D0 are described in 2 Such backgrounds are also present in the other channels, but at a much lower fraction of the total background. Hobbs, Neubauer, and Willenbrock: Tests of the standard electroweak model at . . . TABLE XXIX. The production cross section and cross-section times branching fraction for the high m...
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This document was uploaded on 09/28/2013.

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