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

Jets with et 25 gev and j j 2 0 the shape and

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Unformatted text preview: ubtracting out the nonmultijet backgrounds. The normalization is scaled up to account for the multijet background contamination in the region ÁðET ; pT Þ < 1:0. The 6~ 6~ shape of the multijet background is fit to an exponential in Mjj to derive a dijet mass template for use in the Mjj unbinned extended likelihood fit performed to extract the diboson signal. The distribution of Ájet observed in the ET 6 data is in good agreement with the expectations as shown in Fig. 40, giving confidence in the validity of the multijet background model. Three Mjj template distributions are used in the fit: the first is V þ jets and t-quark production and is taken from Monte Carlo simulation; the second is the multijet template, where the slope and normalization are Gaussian constrained to their previously measured values; and the third template describes the signal. The signal shape is comprised of the WW , WZ, and ZZ distributions obtained from a Gaussian þ polynomial fit to the signal Monte Carlo simulation where the mean and the width of the Gaussian distribution are linearly dependent on the JES. The uncertainty associated with the JES is the dominant source of systematic uncertainty of the diboson cross-section measurement. Figure 41 shows the fit result and a comparison between the expected signal and data after background subtraction. The signal significance is reported to be greater than 5:3 from the background-only hypothesis. This represents the first observation in hadronic collisions of the production of weak gauge boson pairs where one boson decays to a dijet final state. The measured cross section is Rev. Mod. Phys., Vol. 84, No. 4, October–December 2012 ðWW þ WZ þ ZZ þ X Þ ¼ 18:0 Æ 2:8ðstatÞ Æ 2:4ðsystÞ Æ 1:1ðlumiÞ pb; × 10 3 6 Data (3.5 fb-1) EWK Uncertainty Background Diboson Signal Events/8GeV/c 2 4 2 0.440 60 80 60 80 100 120 140 160 100 120 140 160 0.2 0 -0.2 40 Dijet mass (GeV/c2) FIG. 41 (color online). Top: Comparison between data and fitted background only. The measured signal is shown unstacked. The band represents the systematic uncertainty due to the shape of EW background as described by Aaltonen et al. (2009a). Bottom: Comparison of the diboson signal (solid line) with the background-subtracted data (points). The dashed lines represent the Æ1 statistical variations on the extracted signal. The band represents the systematic uncertainty due the EW shape. Hobbs, Neubauer, and Willenbrock: Tests of the standard electroweak model at . . . 1504 TABLE XIX. Tevatron. A summary of EW gauge boson cross-section measurements and theory expectations during Run II and the Fermilab Process R Channel " pp ! W þ X ! ‘ þ X (E > 7 GeV, ÁR‘; > 0:7) T (E > 8 GeV, ÁR‘; > 0:7) T " pp ! Z þ X ! ‘‘ þ X (E > 7 GeV, ÁR‘; > 0:7, T M‘‘ > 40 GeV=c2 ) (E > 7 GeV, ÁR‘; > 0:7, T M‘‘ > 30 GeV=c2 ) " pp ! Z þ X !  þ X (E > 90 GeV) T " pp...
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