Measurement of W+W− Production and Search for the Higgs Boson in pp Collisions at sqrt(s) = 7 TeV

Main Results

A measurement of W+W production in pp collisions at sqrt(s) = 7 TeV and a search for the Higgs boson are reported. The W+W- candidates are selected in events with two leptons, either electrons or muons. The measurement is performed using LHC data recorded with the CMS detector, corresponding to an integrated luminosity of 36 pb−1. The pp → W+W cross section is measured to be 41.1 Â± 15.3 (stat) Â± 5.8 (syst) Â± 4.5 (lumi) pb, consistent with the standard model prediction. Limits on WWγ and WWZ anomalous triple gauge couplings are set. The search for the standard model Higgs boson in the W+W decay mode does not reveal any evidence of excess above backgrounds. Limits are set on the production of the Higgs boson in the context of the standard model and in the presence of a sequential fourth family of fermions with high masses. In the latter context, a Higgs boson with mass between 144 and 207 GeV/c2 is ruled out at 95% confidence level.

Figures from CMS-EWK-10-009-004

Figure Label Description
Figure1a pdf, eps, png Jet multiplicity distribution after all W+W selection criteria, except the top veto and jet veto requirements.
Figure1b pdf, eps, png Dilepton mass distribution for the events passing the WW final selections, except the Z mass veto.
Figure2 pdf, eps, png Leading lepton pT distribution in data overlaid with predictions from the SM simulation, background only simulation (Bkg in the figure) and the simulation with large anomalous couplings (aTGC in the figure).
Figure3a pdf, eps, png Limits on anomalous Triple Gauge Coupling in HIZG parameterization: 68% (solid blue lines) and 95% C.L. (dotted blue lines) as well as the central value (point) and one-dimensional 95% C.L. limits (red lines) using unbinned fits, for âˆ†κ = 0.
Figure3b pdf, eps, png Limits on anomalous Triple Gauge Coupling in HIZG parameterization: 68% (solid blue lines) and 95% C.L. (dotted blue lines) as well as the central value (point) and one-dimensional 95% C.L. limits (red lines) using unbinned fits, for âˆ†g1Z = 0
Figure4 pdf, eps, png Azimuthal angular separation between the two selected leptons after W+W selection, for mH = 160 GeV/c2 SM Higgs signal and for backgrounds. The area marked as W+W corresponds to the nonresonant contribution.
Figure5a pdf, eps, png BDT outputs for Higgs boson signal and for backgrounds, for mH = 160 GeV/c2. The Higgs boson event yield is normalized to the SM expectation. The area marked as W+W corresponds to the nonresonant contribution.
Figure5b pdf, eps, png BDT outputs for Higgs boson signal and for backgrounds, for mH = 200 GeV/c2. The Higgs boson event yield is normalized to the fourth family scenario. The area marked as W+W corresponds to the nonresonant contribution.
Figure6a pdf, eps, png 95% mean expected and observed C.L. upper limits on the cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-600 GeV/c2 using cut-based event selection. Results are obtained using a Bayesian approach. The expected cross sections for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results.
Figure6b pdf, eps, png 95% mean expected and observed C.L. upper limits on the cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-600 GeV/c2 using multivariate BDT event selection. Results are obtained using a Bayesian approach. The expected cross sections for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results.

Figure Files Description
pdf, eps, png Transverse momentum of the most energetic lepton after the W+W selection for SM Higgs signal and background.
pdf, eps, png Transverse momentum of the second most energetic lepton after the W+W selection for SM Higgs signal and background.
pdf, eps, png Dilepton mass distribution for the events passing the W+W selection for SM Higgs signal and background.

 pdf, eps, png 95% mean expected and observed C.L. upper limits on the cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-250 GeV/c2 using cut-based event selection. Results are obtained using a Bayesian approach. The expected cross sections for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results. pdf, eps, png 95% mean expected and observed C.L. upper limits on the cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-600 GeV/c2 using cut-based event selection. Results are obtained using a hybrid frequentist-bayesian approach and the CLs construction. The expected cross sections for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results. pdf, eps, png 95% mean expected and observed C.L. upper limits on the cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-250 GeV/c2 using cut-based event selection. Results are obtained using a hybrid frequentist-bayesian approach and the CLs construction. The expected cross sections for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results. pdf, eps, png 95% mean expected and observed C.L. upper limits on the cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-250 GeV/c2 using multivariate BDT event selection. Results are obtained using a Bayesian approach. The expected cross sections for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results. pdf, eps, png 95% mean expected and observed C.L. upper limits on the cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-600 GeV/c2 using multivariate BDT event selection. Results are obtained using a hybrid frequentist-bayesian approach and the CLs construction. The expected cross sections for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results. pdf, eps, png 95% mean expected and observed C.L. upper limits on the cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-250 GeV/c2 using multivariate BDT event selection. Results are obtained using a hybrid frequentist-bayesian approach and the CLs construction. The expected cross sections for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results.

 pdf, eps, png Observed and expected 95% CL limits on the ratios to the SM cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-250 GeV/c2 using multivariate BDT event selection. Results are obtained using a Bayesian approach. The expected ratios for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results. pdf, eps, png Observed and expected 95% CL limits on the ratios to the SM cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-600 GeV/c2 using multivariate BDT event selection. Results are obtained using a Bayesian approach. The expected ratios for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results. pdf, eps, png Observed and expected 95% CL limits on the ratios to the SM cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-250 GeV/c2 using multivariate BDT event selection. Results are obtained using a hybrid frequentist-bayesian approach and the CLs construction. The expected ratios for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results. pdf, eps, png Observed and expected 95% CL limits on the ratios to the SM cross section (H) Â· BR(H → W+W- → 2l 2nu ) for masses in the range 120-600 GeV/c2 using multivariate BDT event selection. Results are obtained using a hybrid frequentist-bayesian approach and the CLs construction. The expected ratios for the SM and for the SM with a fourth-fermion family cases (SM4) are also presented. The dash line indicates the mean of the expected results. png Di-electron WW candidate. png Electron-muon WW candidate.

Topic attachments
I Attachment History Action Size Date Who Comment
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Topic revision: r12 - 2012-03-10 - ChristophPaus

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