CMS-PAS-HIG-17-004

CMS-PAS-HIG-17-004
Search for Higgs boson production in association with top quarks in multilepton final states at $\sqrt{s}= $ 13 TeV
CMS Collaboration
March 2017

Abstract: A search for the production for a standard model Higgs boson in association with a top quark pair ($\mathrm{t}\overline{\mathrm{t}}\mathrm{H}$) is presented. The analysis is based on pp collision data collected by the CMS experiment at a center of mass energy of $\sqrt{s}= $ 13 TeV in 2016, and corresponding to an integrated luminosity of 35.9 fb$^{-1}$. We target final states where the Higgs boson decays to $\mathrm{WW}^{}$, $\mathrm{ZZ}^{}$ or $\tau\tau$, and at least one of the top quarks decays leptonically, by selecting events with two leptons of the same charge, three leptons or at least four leptons, and b-jets. We obtain a best fit $\mathrm{t}\overline{\mathrm{t}}\mathrm{H}$ yield of 1.5 $\pm$ 0.5 times the standard model prediction, with an observed (expected) significance of 3.3$\sigma$ (2.5$\sigma$), by the combination of these results with those obtained from the 2015 dataset.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	Additional Figures	References	CMS Publications

Figures
png pdf	Figure 1: Possible Feynman diagrams for $ {{\mathrm{ t } {}\mathrm{ \bar{t} } } \mathrm{ H } } $ production at the LHC, where the Higgs boson decays to $W\mathrm{ W } ^{}$ (left) or ${\mathrm{ Z } } {\mathrm{ Z } } ^{}$ (right). Subsequent W and Z decays are shown by representing examples of leptonic final states.
png pdf	Figure 1-a: Feynman diagram for $ {{\mathrm{ t } {}\mathrm{ \bar{t} } } \mathrm{ H } } $ production at the LHC, where the Higgs boson decays to $W\mathrm{ W } ^{*}$. Subsequent W and Z decays are shown by representing examples of leptonic final states.
png pdf	Figure 1-b: Feynman diagram for $ {{\mathrm{ t } {}\mathrm{ \bar{t} } } \mathrm{ H } } $ production at the LHC, where the Higgs boson decays to ${\mathrm{ Z } } {\mathrm{ Z } } ^{*}$. Subsequent W and Z decays are shown by representing examples of leptonic final states.
png pdf	Figure 2: Same-sign dilepton channel; top row: distribution in the categories used for the fit, number of jets, number of jets passing the medium working point of the CSV tagger; bottom row: distributions of the BDT classifier outputs. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 2-a: Same-sign dilepton channel; distribution in the categories used for the fit. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 2-b: Same-sign dilepton channel; distribution in the number of jets. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 2-c: Same-sign dilepton channel; distribution in the number of jets passing the medium working point of the CSV tagger. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 2-d: Same-sign dilepton channel; distribution of the BDT (ttH,tt) classifier output. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 2-e: Same-sign dilepton channel; distribution of the BDT (ttH,ttV) classifier output. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 3: Three lepton channel; top row: distribution in the categories used for the fit, number of jets, number of jets passing the medium working point of the CSV tagger; bottom row: distributions of the BDT classifier outputs. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 3-a: Three lepton channel; distribution in the categories used for the fit. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 3-b: Three lepton channel; distribution in the number of jets. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 3-c: Three lepton channel; distribution in the number of jets passing the medium working point of the CSV tagger. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 3-d: Three lepton channel; distribution of the BDT (ttH,tt) classifier output. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 3-e: Three lepton channel; distribution of the BDT (ttH,ttV) classifier output. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 4: Combination of the BDT classifier outputs in the bins used for signal extraction, for the same-sign dilepton (left) and three-lepton (right) channels. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 4-a: Combination of the BDT classifier outputs in the bins used for signal extraction, for the same-sign dilepton channel. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 4-b: Combination of the BDT classifier outputs in the bins used for signal extraction, for the three-lepton channel. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Figure 5: Minimum mass of opposite-sign (OS) lepton pairs in the 4L category, without any selection on lepton flavor (all-flavor, AF). The distribution is shown after the fit to the data, with all processes constrained to the SM expectation.

Tables
png pdf	Table 1: Yields for expected signal and background processes, and observed yields in data, for the 2LSS (top), 3L and 4l (bottom) channels. The predictions for the non-prompt lepton and charge mis-measurement contributions are extracted from data. Yields are shown after a fit to data, with all processes constrained to the SM expectation.
png pdf	Table 2: Asymptotic 95% CL upper limits on $\mu $ under the background-only hypothesis.
png pdf	Table 3: Best fit of the signal strength parameter.

Summary

A search for the production of a SM Higgs boson in association with a top anti-top quark pair has been presented. The analysis is based on pp collision data collected by the CMS experiment in 2016, and corresponding to an integrated luminosity of 35.9 fb$^{-1}$. We target events where the Higgs boson decays to $\mathrm{WW}^{*}$, $\mathrm{ZZ}^{*}$ or $\tau\tau$ by requiring with two same-sign leptons or at least three leptons in the final state. Results are combined with those obtained from the 2015 dataset. The observed (expected) best fit ${\mathrm{ t \bar{t} }\mathrm{ H }} $ yield is 1.5$_{-0.5}^{+0.5}$ (1.0$_{-0.4}^{+0.5}$) times the SM prediction, corresponding to a significance of 3.3$\sigma$ (2.5$\sigma$).

Additional Figures
png pdf	Additional Figure 1: Best fit signal strength for the 2016 analysis alone in different analysis channels (a) and with statistical and systematic uncertainties separately displayed (b).
png pdf	Additional Figure 1-a: Best fit signal strength for the 2016 analysis alone in different analysis channels.
png pdf	Additional Figure 1-b: Best fit signal strength for the 2016 analysis alone in different analysis channels, with statistical and systematic uncertainties separately displayed.
png pdf	Additional Figure 2: Event yields in the bins used for the signal extraction fit in the 2LSS and 3L channels. Each block of 8 bins in 2LSS, 5 bins in 3L corresponds to an analysis category, with the same ordering as in the figures presented in the PAS. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Additional Figure 2-a: Event yields in the bins used for the signal extraction fit in the 2LSS channel. Each block of 8 bins corresponds to an analysis category, with the same ordering as in the figures presented in the PAS. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Additional Figure 2-b: Event yields in the bins used for the signal extraction fit in the 3L channel. Each block of 5 bins corresponds to an analysis category, with the same ordering as in the figures presented in the PAS. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Additional Figure 3: Distribution of the hadronic top and Higgs jet tagger BDT scores in the 2LSS channel. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Additional Figure 3-a: Distribution of the hadronic top tagger BDT score in the 2LSS channel. The distribution is shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Additional Figure 3-b: Distribution of the Higgs jet tagger BDT score in the 2LSS channel. The distribution is shown after the fit to the data, with all processes constrained to the SM expectation.
png pdf	Additional Figure 4: Distribution of the likelihood ratio of matrix element weights in the 3L channel. The distributions are shown after the fit to the data, with all processes constrained to the SM expectation.

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