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

Backgrounds except those from multijet events in

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: fficiency, jet identification efficiency, the  lepton energy calibration, and background cross sections. The systematic uncertainties DØ 5.4 fb-1 10 4 103 102 5. H ! WW à For mH * 135 GeV=c2 , the dominant Higgs decay is to W boson pairs. Below the W pair production threshold, one of the W bosons will be off shell which leads to lower pT leptons from the W à decay. The most sensitive high mass Higgs channel is gg ! H ! WW ðÃÞ ! ‘‘, where the two charged leptons in the final state are of opposite charge. In addition to the dominant ggH process, other Higgs production processes that contribute at the Tevatron are VBF and VH , where V  ðW; ZÞ. Early Tevatron Run II searches for a high mass Higgs boson (Abulencia et al., 2006c; Abazov et al., 2006b) focused mainly on the ggH process and exploiting the angular correlation between final-state charged leptons due to the scalar (spin-0) nature of the SM Higgs. In a more recent analysis (Aaltonen et al., 2009h), CDF used a NN technique to search for a Higgs-boson signal in dilepton þ ET events 6 having either zero or one reconstructed jet. Several kinematic variables, including the results of matrix element calculations that combined charged-lepton and ET information, were used 6 as inputs to the NN. The CDF and D0 searches for H ! WW ðÃÞ by Aaltonen et al. (2010c) and Abazov et al. (2010b), respectively, significantly increase their sensitivities compared to previous results through the use of additional data, topologies arising DØ 5.4 fb-1 b) 10 105 which affect the shape for the bb analysis are the jet energy resolutions, the jet energy calibration, and the b-tagging efficiencies. For the jj analysis only the multijet background had a shape dependence. The systematic uncertainties, expressed as a fraction of the related source, range between 3% and 30%. For example, the W þ hf cross-section systematic is 30% of the W þ hf background, but because the background is roughly 50% of the total background in the bb channel, the effective systematic is roughly 15%. Predicted background and signal levels and observed yields for the two searches are shown in Table XXXVIII assuming a signal mass of MH ¼ 115 GeV=c2 . The distributions or MJJ and the output from the Z þ jets NN NNZ are used as inputs to the limit setting program for the bb and jj searches, respectively. The distributions are shown in Fig. 62, and the resulting limits are shown in Table XXXIX. c) Data Bkgd. syst. Signal Z+jets Diboson W+jets Multijet tt DØ 5.4 fb-1 3 Events / 0.1 a) Events / 0.2 rad Events / 10 GeV 106 1521 102 10 103 102 10 10 0 50 100 150 200 Dilepton Mass (GeV) 0 0.5 1 ∆φ(l,l ) (rad) 1.5 2 0 0.2 0.4 0.6 0.8 1 NN Output FIG. 63 (color online). For the D0 H ! WW ðÃÞ analysis (Abazov et al., 2010b), the (a) dilepton invariant mass after preselection; (b) Áð‘; ‘Þ angle after final selection; and (c) neural network output after final selection. The signal is shown for mH ¼ 165 GeV. Th...
View Full Document

This document was uploaded on 09/28/2013.

Ask a homework question - tutors are online