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

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Unformatted text preview: anomalous TGC limits are shown in Fig. 13. A LO simulation (Baur and Berger, 1990) of the W signal is used with NLO corrections (Baur and Berger, 1993) applied to the photon ET spectrum. The one-dimensional limits at 95% confidence level (C.L.) are À0:51 < Á < 0:51 and À0:12 <  < 0:13 for à ¼ 2:0 TeV. The SM W production involves interference between the amplitudes for a photon radiated off of an incoming quark (QED initial-state radiation) and the photon produced from the WW vertex. This interference leads to a zero amplitude for the SM in the photon angular distribution (Brown, Sahdev, and Mikaelian, 1979; Mikaelian, Samuel, and Sahdev, 1979; Goebel, Halzen, and Leveille, 1981; Brodsky and Brown, 1982). In W production, the radiation amplitude zero (RAZ) manifests itself as a dip at $ À 1=3 in the chargedsigned rapidity difference Q‘  Áy between the observed photon and the charged lepton from decay of the W boson (Baur, Errede, and Landsberg, 1994). Experimentally, the pseudorapidity difference Á is used in place of the rapidity difference Áy, since it involves only the production angle  with respect to the beam line [ ¼ À lnð tanð=2ÞÞ] and is a very good approximation to Áy in the limit of massless particles. Using the same data they used to limits on WW anomalous TGCs, D0 made the first detailed study of the Q‘  Áy to search for the RAZ effect (Abazov et al., 2008b). Figure 14(a) shows the Q‘  Áy distribution of data compared with the SM expectation, which has a 15% 2 TABLE VI. Summary of the W ! ‘ CDF (Acosta et al., 2005b) and D0 (Abazov et al., 2005a) cross-section analyses compared with the theory (Baur and Berger, 1993). For the CDF analysis, the luminosities with and without parentheses correspond to central and forward leptons, respectively. The theory cross section is the NLO calculation (in pb) from Baur and Berger, 1993. D0 analysis CDF analysis e  e  Ldt W þ jetðsÞ ‘eX W !  Z ! ‘‘ 0.16 59 Æ 5 1:7 Æ 0:5 0:42 Æ 0:02 ÁÁÁ 0.13 62 Æ 5 0:7 Æ 0:2 1:9 Æ 0:2 6:9 Æ 0:7 0.20 (0.17) 60 Æ 18 ÁÁÁ 1:5 Æ 0:2 6:3 Æ 0:3 0.19 (0.18) 28 Æ 8 ÁÁÁ 2:3 Æ 0:2 17:4 Æ 1:0 Total background Nobserved   BR (pb) Theory   BR 61 Æ 5 71 Æ 5 112 161 13:9 Æ 3:4 15:2 Æ 2:5 16:0 Æ 0:4 R ðfbÀ1 Þ Rev. Mod. Phys., Vol. 84, No. 4, October–December 2012 67 Æ 18 47 Æ 8 195 128 19:4 Æ 3:6 16:3 Æ 2:9 19:3 Æ 1:4 Hobbs, Neubauer, and Willenbrock: Tests of the standard electroweak model at . . . 50 -1 Data Candidates SM MC + Background (κ=1, λ=0) AC MC + Background (κ=1, λ=0.2) Background 102 Events 10 1 (a) DØ, 0.7 fb-1 Data (total uncertainties) 40 Events/(0.70) (a) DØ, 0.7 fb 1489 SM (systematic uncertainties) 30 20 10 10-1 0 100 150 200 250 300 -4 -3 -2 -1 Photon ET (GeV) 800 (b) DØ, 0.7 fb -1 0.4 Experiments λγ SM MUH 700 0.2 0 -0.2 600 1 2 3 4 500 -4 -3 -2 -1 0 1 2 3 4 Q × ∆η 400 300 (b) DØ, 0.7 fb-1 200 100 -0.4 0 0 Q × ∆η Small Max Bin Dip Bin 50 0.5 1...
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This document was uploaded on 09/28/2013.

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