TOP-13-017
Search for flavor-changing neutral Higgs-boson production in processes involving top-quark pairs in pp collisions at sqrt(s) = 8 TeV

Abstract

A search for top-quark decays via Higgs-boson-mediated flavor-changing neutral current in events compatible with the trilepton and same-sign dilepton topologies of pp → tt → Hc + Wb events are presented. The search is performed with a data sample corresponding to an integrated luminosity of 19.7 fb-1 of proton-proton collisions at a center-of-mass energy of 8 TeV collected with the CMS detector at the LHC. The observed number of events agrees with the SM prediction, and no evidence for flavor-changing neutral Higgs boson production in top-quark decays is found. The estimated 95% confidence level observed and expected upper limits on the t → Hc branching fraction are respectively 0.93% and 0.89%. This corresponds to an upper limit on top-charm flavor-violating Higgs Yukawa coupling of √(|λHtc|2 + |λHct|2) < 0.18.

Public Document

The document CMS-PAS-TOP-13-017 is available here.

Results

Figure Caption
leading_b-jet_pt.png leading_b-jet_eta.png lead_lepton_pt.png lead_lepton_eta.png seclead_lepton_pt.png Feynman diagrams for different final states from the Higgs-mediated flavor-changing top quark decay. Click on the figures to retrieve them in PDF format
Figure 2a: MET distribution in the trilepton channel as observed in data (points with error bars) and as predicted by the SM backgrounds (solid colors) for an integrated luminosity of 19.7 fb-1. The overall background uncertainty is shown in stippled black. The expected signal assuming a B(t -> Hc) of 3% is shown in the unfilled histogram.
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Figure 2b: MET distribution in the same-sign dilepton channel as observed in data (points with error bars) and as predicted by the SM backgrounds (solid colors) for an integrated luminosity of 19.7 fb-1. The overall background uncertainty is shown in stippled black. The expected signal assuming a B(t -> Hc) of 3% is shown in the unfilled histogram.
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Figure 2c: HT distribution in the trilepton channel as observed in data (points with error bars) and as predicted by the SM backgrounds (solid colors) for an integrated luminosity of 19.7 fb-1. The overall background uncertainty is shown in stippled black. The expected signal assuming a B(t -> Hc) of 3% is shown in the unfilled histogram.
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Figure 2d: HT distribution in the same-sign dilepton channel as observed in data (points with error bars) and as predicted by the SM backgrounds (solid colors) for an integrated luminosity of 19.7 fb-1. The overall background uncertainty is shown in stippled black. The expected signal assuming a B(t -> Hc) of 3% is shown in the unfilled histogram.
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Figure 3: Trilepton invariant mass versus opposite-sign (OS) dilepton invariant mass in the trilepton channel after the basic event selection for signal, data and estimated background, from left to right.
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Figure 4a: Jet multiplicity in the samples featuring three identified leptons after rejecting events with Z bosons. The data are represented by the points with error bars and the unfilled histogram shows the expected signal assuming B(t -> Hc) is equal to 3%. The dominant backgrounds are represented with solid colors.
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Figure 4b: Jet multiplicity in the samples featuring two identified, same-sign leptons after rejecting events with Z bosons. The data are represented by the points with error bars and the unfilled histogram shows the expected signal assuming B(t -> Hc) is equal to 3%. The dominant backgrounds are represented with solid colors.
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Figure 5a: MET distribution in the trilepton channel as observed in data (points with error bars) and as predicted by the SM backgrounds (solid colors) after rejecting events containing Z bosons, requiring at least two jets and the basic event selection. The overall background uncertainty is shown in stippled black. The expected signal assuming a B(t -> Hc) of 3% is shown in the unfilled histogram.
PDF PNG
Figure 5b: MET distribution in the same-sign dilepton channel as observed in data (points with error bars) and as predicted by the SM backgrounds (solid colors) after rejecting events containing Z bosons, requiring at least two jets and the basic event selection. The overall background uncertainty is shown in stippled black. The expected signal assuming a B(t -> Hc) of 3% is shown in the unfilled histogram.
PDF PNG
Figure 5c: HT distribution in the trilepton channel as observed in data (points with error bars) and as predicted by the SM backgrounds (solid colors) after rejecting events containing Z bosons, requiring at least two jets and the basic event selection described in Section 2. The overall background uncertainty is shown in stippled black. The expected signal assuming a B(t -> Hc) of 3% is shown in the unfilled histogram.
PDF PNG
Figure 5d: HT distribution in the same-sign dilepton channel as observed in data (points with error bars) and as predicted by the SM backgrounds (solid colors) after rejecting events containing Z bosons, requiring at least two jets and the basic event selection. The overall background uncertainty is shown in stippled black. The expected signal assuming a B(t -> Hc) of 3% is shown in the unfilled histogram.
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Table Caption
Table 2a: Event yields for trilepton category assuming B(t→ Hc) = 1%.
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Table 2b: Event yields for same-sign dilepton category assuming B(t→ Hc) = 1%.
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Table 3: Upper limits at 95% CL on branching fraction of t→Hq for three leptons, same-sign dilepton, and combined selections.
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AndreasMeyer - 2015-03-15

Topic attachments
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PDFpdf AllJetMult_3l_Zveto.pdf r1 manage 15.3 K 2015-03-06 - 03:10 NateOdell  
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PDFpdf AllJetMult_ss_Zveto.pdf r1 manage 15.2 K 2015-03-06 - 03:10 NateOdell  
PNGpng AllJetMult_ss_Zveto.png r3 r2 r1 manage 135.7 K 2015-03-17 - 20:20 AndreasMeyer  
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PNGpng HT_3l_jet.png r3 r2 r1 manage 242.0 K 2015-03-17 - 20:20 AndreasMeyer  
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PNGpng HT_3l_pre.png r3 r2 r1 manage 194.8 K 2015-03-17 - 20:20 AndreasMeyer  
PDFpdf HT_ss_jet.pdf r1 manage 17.9 K 2015-03-12 - 19:58 NateOdell  
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PDFpdf HT_ss_pre.pdf r1 manage 18.1 K 2015-03-12 - 19:58 NateOdell  
PNGpng HT_ss_pre.png r3 r2 r1 manage 188.6 K 2015-03-17 - 20:20 AndreasMeyer  
PDFpdf Met_3l_jet.pdf r1 manage 16.2 K 2015-03-12 - 19:58 NateOdell  
PNGpng Met_3l_jet.png r3 r2 r1 manage 223.7 K 2015-03-17 - 20:20 AndreasMeyer  
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PNGpng Met_3l_pre.png r3 r2 r1 manage 185.9 K 2015-03-17 - 20:20 AndreasMeyer  
PDFpdf Met_ss_jet.pdf r1 manage 18.0 K 2015-03-12 - 19:58 NateOdell  
PNGpng Met_ss_jet.png r3 r2 r1 manage 269.4 K 2015-03-17 - 20:20 AndreasMeyer  
PDFpdf Met_ss_pre.pdf r1 manage 18.2 K 2015-03-12 - 19:58 NateOdell  
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