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

wbw b where 6 two charged leptons result from the w

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Unformatted text preview: :27 Æ 0:28 Æ À 0:88 Æ 0:01 Æ 0:09 Æ 0:05 0:44 Æ 0:05 Æ 0:15 Æ 0:03 0:12 Æ 0:01 Æ 0:02 Æ 0:01 2:65 Æ 0:28 Æ 0:33 Æ 0:09 9:75 Æ 0:03 Æ 0:31 Æ 0:59 12:41 Æ 0:28 Æ 0:45 Æ 0:67 16 Total background WZ Total expected Observed important for a number of reasons. The production of WZ involves the WWZ TGC as shown in the s-channel diagram in Fig. 22. Unlike WW production which involves a combination of the WW and WWZ couplings such that assumptions regarding their relation must be invoked to interpret any anomalies observed in the data, the WZ production characteristics can be used to make a model-independent test of the SM WWZ coupling. Stated differently, in WZ production measurements, a direct measure of the WZ coupling independent of the W coupling can be made and compared to the SM predictions. The fully leptonic decay mode of WZ provides a clean SM trilepton signal which is analogous to the so-called golden mode for discovering supersymmetry (SUSY) at the ~1 ~2 Tevatron via chargino-neutralino production (Æ 0 ) and decay. Therefore, an observation of the SM WZ trilepton signal represents an important experimental milestone in demonstrating sensitivity to the SUSY golden mode and other new physics signatures in multileptons. Prior to the start of Run II at the Tevatron, WZ production had not been observed. ThepNLO WZ cross-section predicffiffi " tion for pp collisions at s ¼ 1:96 TeV is 3:7 Æ 0:3 pb (Campbell and Ellis, 1999). In October 2006, WZ production was first observed by the CDF Collaboration in the three charged lepton þ ET final state using 1:1 fbÀ1 of integrated 6 luminosity (Abulencia et al., 2007b). The most sensitive previous search for WZ production was reported by the WZ Events / 2.5 GeV 10 Zγ ZZ Z+jets tt 1 10 -1 Data 7 10 -2 Zγ 6 Data Zγ WZ 8 Events / 4 GeV/c2 Data 10 2 ZZ 5 WZ ZZ Z+jets tt Z+jets 6 tt 5 4 3 2 1 0 0 10 20 30 40 50 60 70 80 90 ET [GeV] Events / 10 GeV/c2 1494 4 3 2 1 0 40 60 80 100 Ml+l- [GeV/c2] 120 140 0 20 40 60 80 100 MW [GeV/c2] T FIG. 23 (color online). Distributions for WZ candidates of (a) the ET , (b) the dilepton invariant mass for the same-flavor opposite-sign 6 dilepton pair closest to the Z mass, and (c) the W transverse mass calculated from the remaining lepton and the ET , for the CDF WZ ! ‘‘‘ 6 analysis. In (a) and (b), the arrows indicate the signal region. From Abulencia et al., 2007b. Rev. Mod. Phys., Vol. 84, No. 4, October–December 2012 Hobbs, Neubauer, and Willenbrock: Tests of the standard electroweak model at . . . CDF analysis Expected Data D0 analysis Expected Data eee ee e  e e ‘t e  ‘t   ‘t e ‘t ‘t  ‘t ‘t 2:7 Æ 0:2 2:0 Æ 0:2 1:5 Æ 0:1 1:2 Æ 0:1 2:0 Æ 0:2 1:3 Æ 0:1 1:1 Æ 0:1 0:5 Æ 0:1 0:2 Æ 0:1 3:5 Æ 0:2 2:7 Æ 0:2 4:2 Æ 0:5 3:4 Æ 0:4 ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ 6 0 1 1 5 2 1 0 0 2 1 8 2 ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ ÁÁÁ backgrounds are suppressed by requiring ET > 25 GeV in the 6 event, consistent...
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This document was uploaded on 09/28/2013.

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