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

2 an electroweak test sample enhanced in w events and

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Unformatted text preview: ining one of the two highest ET jets satisfies a lower purity (loose) identification requirement. Events without an additional tag are denoted as single tagged. For the tight requirement, the per jet identification efficiency is 50% with a misidentification probability of 0.5%. The loose requirement has an efficiency of 70% with a misidentification probability of 6.5%. Table XXXVII shows the data yield and prediction for the initial preselection and for the single- and double-tagged samples and the expected Higgs-boson signal for a Higgs boson of mass 115 GeV=c2 . " The backgrounds from tt, W þ jets, Z þ jets, and diboson processes are estimated using simulated events. These results are validated using the EW enriched control sample. The shape of the multijet background is taken from the multijet modeling sample, and the normalization is determined by forcing the number of multijet events plus the number of SM predicted background events to equal the data yield in the preselection sample. This procedure is validated by comparing the prediction with the multijet enriched sample. The signal-to-background separation is then further improved using BDTs. For each mH considered, a multijet boosted decision tree (MJ BDT) with 23 input variables is Rev. Mod. Phys., Vol. 84, No. 4, October–December 2012 trained on Higgs signal and multijet backgrounds. Events which have a MJ BDT output greater than 0.6 are retained. These events are then input to a second BDT (SM BDT) trained on the remaining backgrounds and Higgs signal events using the same 23 variables input to the MJ BDT. Figure 60 shows the BDT outputs for the data, predicted background, and signal. The agreement between data and prediction is good. Limits are extracted by fitting signal and background SM BDT outputs to the data distribution using the same modified frequentist algorithm as was used for the previously described D0 results. Figure 61 shows the Higgs cross-section limits from the D0 analysis. The systematic uncertainties for the D0 result are dominated by similar sources as for the CDF analysis. The D0 jet energy calibration systematic is <10%, and the background normalization systematic varies between 6% and 20%. D0 also reports additional systematic uncertainties from luminosity, trigger, and identification efficiencies and b-tagging FIG. 60 (color online). The outputs for the (a) MJ BDT, (b) the SM BDT for the single-tagged channel, and (c) the SM BDT for the double-tagged channel for the D0 VH ! ET bb analysis. 6 Hobbs, Neubauer, and Willenbrock: Tests of the standard electroweak model at . . . 30 25 Observed Limit Expected Limit DØ, 5.2 fb-1 TABLE XXXVIII. Expected and observed yields for the D0 VH ! bb and VH ! jj searches. Only statistical uncertainties are shown. Search channel 20 Source 15 10 5 0 100 105 110 115 120 125 130 135 140 145 150 mH (GeV/c2) FIG. 61 (color online). The expected and observed 90% C.L. upper bounds on the Higgs-boson production cross s...
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