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

Subleading trailing lepton pt is also included in a

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Unformatted text preview: ous couplings (see Fig. 20 for the 1D projections). There are several ways to relate the WW and WWZ couplings in the presence of new physics. This is a convenient prescription to reduce the number of parameters since WW production involves both WW and WWZ couplings. Enforcing SUð2ÞL  Uð1ÞY symmetry introduces two relationships between the remaining parameters: Z ¼ gZ À 1 ð À 1Þtan2 W and Z ¼  , reducing the number of free parameters to three (De Rujula et al., 1992; Hagiwara et al., 1993). Alternatively, enforcing equality between the WW and WWZ vertices (WW ¼ WWZ) such that  ¼ Z ,  ¼ Z , and gZ ¼ 1 reduces the number of free parameters 1 to two. In the D0 analysis, the one-dimensional 95% C.L. limits for à ¼ 2 TeV are determined to be À0:54 < Á < 0:83, À0:14 <  ¼ Z < 0:18, and À0:14 < ÁgZ < 0:30 under 1 the SUð2ÞL  Uð1ÞY conserving constraints, and À0:12 < Á ¼ ÁZ < 0:35, with the same  limits as above, under the WW ¼ WWZ constraints. One- and two-dimensional 95% C.L. limits are shown in Fig. 21. In the CDF analysis, only 1D limits on the anomalous coupling parameters under the assumption of SUð2ÞL  Uð1ÞY invariance are reported. The expected and observed 95% confidence limits are shown in Table XI where it is evident that the limits are weaker than expected. The probability of observing these limits in the presence of only SM WW production ranges from 7.1% to 7.6% depending on the coupling parameters (Z , Á , ÁgZ ) 1 and are consistent with a statistical fluctuation of SM physics. The WZ final state is not available in eþ eÀ collisions at " LEP but can be produced in pp collisions at the Tevatron. The study of associated production of a W and Z boson is 0 -0.1 -0.4 Expected Observed Expected Observed  ¼ Z 5. WZ 0.1 λγ=λZ 0.2 ∆ gZ 0 -0.2 -0.4 TABLE XI. Expected and observed limits from the CDF WW ! ‘‘ analysis searching for anomalous TGCs assuming two different values of the form factor scale à (Aaltonen et al., 2010a). For each coupling limit set, the two other couplings are fixed at their SM values. Values of the couplings outside of the given observed range are excluded at the 95% confidence level (C.L.). 10 0 1493 -0.2 -0.4 -0.2 0 0.2 0.4 λγ -0.4 -0.2 0 0.2 0.4 ∆κγ=∆κZ FIG. 21. One- and two-dimensional 95% C.L. limits for the D0 WW ! ‘‘ analysis (Abazov et al., 2009e) when enforcing SUð2ÞL  Uð1ÞY symmetry at à ¼ 2 TeV, for (a) Á vs  , (b) Á vs ÁgZ , and (c)  vs ÁgZ , each when the third free 1 1 coupling is set to its SM value; limits when enforcing the WW ¼ WWZ constraints are shown in (d). The curve represents the twodimensional 95% C.L. contour and the ticks along the axes represent the one-dimensional 95% C.L. limits. An asterisk (*) marks the point with the highest likelihood in the two-dimensional plane. Rev. Mod. Phys., Vol. 84, No. 4, October–December 2012 FIG. 22. Leading-order (a) t-channel and (...
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This document was uploaded on 09/28/2013.

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