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

From simulated processes for the cdf analysis from

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Unformatted text preview: þ WZ production in the lepton þ jets channel. The measured cross section using the ME method is ðWV þ XÞ ¼ 17:7 Æ 3:1ðstatÞ Æ 2:4ðsystÞ pb: it was used in the WW ! ‘‘ analysis and has been used in a number of different CDF and D0 analyses. The normalization of the Z þ jets background is based on " the measured cross section (Acosta et al., 2005d). The tt and single-top background normalizations are from the NLO predicted cross sections (Cacciari et al., 2008). The efficien" cies for the Z þ jets, tt, and single-top backgrounds are estimated from simulation. The normalization of the multijet background is estimated by fitting the ET spectrum in data to 6 the sum of all contributing processes, where the multijet and W þ jets normalizations float in the fit. In the final signal extractions from both methods, the multijet background is Gaussian constrained to the result of this ET fit and the 6 W þ jets background is left unconstrained. In the dijet method, the signal fraction in the data is estimated by performing a 2 fit to the dijet invariant mass spectrum, separately for electron and muon events. Figure 33 shows the dijet invariant mass distribution of data compared to the fitted signal and background contributions. The observed (expected) signal significance using the dijet method is 4:6 (4:9) for electrons and muons combined. The measured cross section is ðWV þ X Þ ¼ 14:4 Æ 3:1ðstatÞ Æ 2:2ðsystÞ pb: In the ME method, the calculated event probabilities are combined into an event probability discriminant EPD ¼ Psignal =ðPsignal þ Pbackground Þ, where Psignal ¼ PWW þ PWZ and Pbackground ¼ PW þjets þ Psingletop . Templates of the EPD generated for all signal and background processes are used in a binned likelihood fit for the signal yield observed in the data, as shown in Fig. 34. Figure 35 shows the dijet mass in bins of EPD, where it can be seen that the low EPD bin Rev. Mod. Phys., Vol. 84, No. 4, October–December 2012 In the Mjj method the largest systematic uncertainties are due to the modeling of the EW and multijet shapes, about 8% and 6%, respectively. In the ME method the uncertainty in the jet energy scale is the largest systematic uncertainty, at about 10%, which includes contributions from both the signal acceptance and the shapes of the signal templates. In the Mjj method this uncertainty is about 6%. The combined cross section for the dijet and ME methods, with consideration of statistical and systematic uncertainties, is ðWV þ XÞ ¼ 16:0 Æ 3:3ðstat þ systÞ pb: Both of the CDF and D0 WW þ WZ cross-section measurements are consistent with the SM NLO expectations. In Aaltonen et al. (2007a), CDF searches for anomalous WW and WWZ couplings using the observed spectrum of the charged lepton pT from a W decay and R Ldt ¼ 0:35 fbÀ1 . Figure 36 shows good consistency between the SM expectation for W boson pT and the data which are used to constrain possible anomalou...
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This document was uploaded on 09/28/2013.

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