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| CMS-PAS-B2G-15-003 | ||
| Search for top quark-antiquark resonances in the all-hadronic final state at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| June 2016 | ||
| Abstract: A search is presented for the production of heavy resonances decaying to top quark-antiquark pairs in the all-hadronic channel. The analysis is performed using 2.6 fb$^{-1}$ of data collected in proton-proton collisions at $\sqrt{s} = $ 13 TeV with the CMS detector. This analysis focuses on high-mass resonances decaying to top quarks with high Lorentz boosts. These highly-boosted top quarks are reconstructed as single jets with substructure corresponding to the t$\rightarrow$bW$\rightarrow$bqq decay. No excess above the expectation from the standard model is observed, and we set limits on the production cross sections of Z' bosons and RS gluons, for signal models with varying widths. For wider Z' signal models, we eclipse previous exclusion limits, excluding Z' bosons with masses up to 3.3 (3.8) TeV, for Z' widths of 10% (30%) of their masses. | ||
| Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1-a:
t-tagging mistag rate as measured with an anti-tag and probe procedure. The red squares indicate the mistag rate measured in QCD simulation. Blue circles indicate the mistag rate measured in data. The contamination from $ {\mathrm{ t \bar{t} } } $ is removed by subtracting simulated $ {\mathrm{ t \bar{t} } } $ events, normalized to expectation. The mistag rate is measured separately for each of the six event categories described in the text. |
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Figure 1-b:
t-tagging mistag rate as measured with an anti-tag and probe procedure. The red squares indicate the mistag rate measured in QCD simulation. Blue circles indicate the mistag rate measured in data. The contamination from $ {\mathrm{ t \bar{t} } } $ is removed by subtracting simulated $ {\mathrm{ t \bar{t} } } $ events, normalized to expectation. The mistag rate is measured separately for each of the six event categories described in the text. |
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Figure 1-c:
t-tagging mistag rate as measured with an anti-tag and probe procedure. The red squares indicate the mistag rate measured in QCD simulation. Blue circles indicate the mistag rate measured in data. The contamination from $ {\mathrm{ t \bar{t} } } $ is removed by subtracting simulated $ {\mathrm{ t \bar{t} } } $ events, normalized to expectation. The mistag rate is measured separately for each of the six event categories described in the text. |
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Figure 1-d:
t-tagging mistag rate as measured with an anti-tag and probe procedure. The red squares indicate the mistag rate measured in QCD simulation. Blue circles indicate the mistag rate measured in data. The contamination from $ {\mathrm{ t \bar{t} } } $ is removed by subtracting simulated $ {\mathrm{ t \bar{t} } } $ events, normalized to expectation. The mistag rate is measured separately for each of the six event categories described in the text. |
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Figure 1-e:
t-tagging mistag rate as measured with an anti-tag and probe procedure. The red squares indicate the mistag rate measured in QCD simulation. Blue circles indicate the mistag rate measured in data. The contamination from $ {\mathrm{ t \bar{t} } } $ is removed by subtracting simulated $ {\mathrm{ t \bar{t} } } $ events, normalized to expectation. The mistag rate is measured separately for each of the six event categories described in the text. |
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Figure 1-f:
t-tagging mistag rate as measured with an anti-tag and probe procedure. The red squares indicate the mistag rate measured in QCD simulation. Blue circles indicate the mistag rate measured in data. The contamination from $ {\mathrm{ t \bar{t} } } $ is removed by subtracting simulated $ {\mathrm{ t \bar{t} } } $ events, normalized to expectation. The mistag rate is measured separately for each of the six event categories described in the text. |
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Figure 2-a:
Final log-scale distributions of $m_{ {\mathrm{ t \bar{t} } } }$ for all six signal regions, with the $\Delta y < $ 1.0 categories shown in the left column and the $\Delta y > $ 1.0 categories in the right. The number of b-tags in the plots increase from zero in the first row to two b-tags in the third row. The shaded region corresponds to the combined systematic and statistical uncertainties on the background model. Signal models have been normalized to a cross section of 1 pb. |
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Figure 2-b:
Final log-scale distributions of $m_{ {\mathrm{ t \bar{t} } } }$ for all six signal regions, with the $\Delta y < $ 1.0 categories shown in the left column and the $\Delta y > $ 1.0 categories in the right. The number of b-tags in the plots increase from zero in the first row to two b-tags in the third row. The shaded region corresponds to the combined systematic and statistical uncertainties on the background model. Signal models have been normalized to a cross section of 1 pb. |
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Figure 2-c:
Final log-scale distributions of $m_{ {\mathrm{ t \bar{t} } } }$ for all six signal regions, with the $\Delta y < $ 1.0 categories shown in the left column and the $\Delta y > $ 1.0 categories in the right. The number of b-tags in the plots increase from zero in the first row to two b-tags in the third row. The shaded region corresponds to the combined systematic and statistical uncertainties on the background model. Signal models have been normalized to a cross section of 1 pb. |
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Figure 2-d:
Final log-scale distributions of $m_{ {\mathrm{ t \bar{t} } } }$ for all six signal regions, with the $\Delta y < $ 1.0 categories shown in the left column and the $\Delta y > $ 1.0 categories in the right. The number of b-tags in the plots increase from zero in the first row to two b-tags in the third row. The shaded region corresponds to the combined systematic and statistical uncertainties on the background model. Signal models have been normalized to a cross section of 1 pb. |
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Figure 2-e:
Final log-scale distributions of $m_{ {\mathrm{ t \bar{t} } } }$ for all six signal regions, with the $\Delta y < $ 1.0 categories shown in the left column and the $\Delta y > $ 1.0 categories in the right. The number of b-tags in the plots increase from zero in the first row to two b-tags in the third row. The shaded region corresponds to the combined systematic and statistical uncertainties on the background model. Signal models have been normalized to a cross section of 1 pb. |
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Figure 2-f:
Final log-scale distributions of $m_{ {\mathrm{ t \bar{t} } } }$ for all six signal regions, with the $\Delta y < $ 1.0 categories shown in the left column and the $\Delta y > $ 1.0 categories in the right. The number of b-tags in the plots increase from zero in the first row to two b-tags in the third row. The shaded region corresponds to the combined systematic and statistical uncertainties on the background model. Signal models have been normalized to a cross section of 1 pb. |
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Figure 3-a:
Expected and observed 95% CL upper limits on the cross section times branching ratio for the four signal models, as a function of the new heavy particle mass. The four models considered are a Z' boson whose width is 1% of its mass (a), a 10% width Z' boson (b), a 30% width Z' boson (c), and an RS KK gluon (d). The solid (dashed) black line gives the observed (median expected) limits, while the one (two) sigma expected limit band is shown in green (yellow). The solid line shows the expected theoretical cross section for the signal process of interest. |
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Figure 3-b:
Expected and observed 95% CL upper limits on the cross section times branching ratio for the four signal models, as a function of the new heavy particle mass. The four models considered are a Z' boson whose width is 1% of its mass (a), a 10% width Z' boson (b), a 30% width Z' boson (c), and an RS KK gluon (d). The solid (dashed) black line gives the observed (median expected) limits, while the one (two) sigma expected limit band is shown in green (yellow). The solid line shows the expected theoretical cross section for the signal process of interest. |
png pdf |
Figure 3-c:
Expected and observed 95% CL upper limits on the cross section times branching ratio for the four signal models, as a function of the new heavy particle mass. The four models considered are a Z' boson whose width is 1% of its mass (a), a 10% width Z' boson (b), a 30% width Z' boson (c), and an RS KK gluon (d). The solid (dashed) black line gives the observed (median expected) limits, while the one (two) sigma expected limit band is shown in green (yellow). The solid line shows the expected theoretical cross section for the signal process of interest. |
png pdf |
Figure 3-d:
Expected and observed 95% CL upper limits on the cross section times branching ratio for the four signal models, as a function of the new heavy particle mass. The four models considered are a Z' boson whose width is 1% of its mass (a), a 10% width Z' boson (b), a 30% width Z' boson (c), and an RS KK gluon (d). The solid (dashed) black line gives the observed (median expected) limits, while the one (two) sigma expected limit band is shown in green (yellow). The solid line shows the expected theoretical cross section for the signal process of interest. |
| Tables | |
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Table 1:
Summary of systematic uncertainties applied to the analysis. |
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Table 2:
Expected background and observed data yields for the six event categorizations used in the final analysis selection. Errors include both the statistical and systematic components. |
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Table 3:
Observed and expected exclusion ranges for resonance masses in each of the signal models tested in the analysis. |
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Table of expected and observed 95% CL cross section limits, for the narrow (1% width) Z' signal hypothesis.:
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Table of expected and observed 95% CL cross section limits, for the wide (10% width) Z' signal hypothesis.:
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Table of expected and observed 95% CL cross section limits, for the extra wide (30% width) Z' signal hypothesis.:
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Table of expected and observed 95% CL cross section limits, for the RS Gluon signal hypothesis.:
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| Summary |
| We have performed the first search for top quark pair resonances in the all-hadronic channel using $\sqrt{s} = $ 13 TeV data from the LHC Run 2. The search uses a new top-tagging algorithm, optimized for Run 2 analyses, using the jet mass from the modified mass-drop tagger and N-subjettiness jet substructure variables along with subjet b-tagging. We estimate the non-top multijet background using a mistag rate measured in a control region depleted of $\mathrm{ t \bar{t} }$ events. No excess above the standard model expectation is observed, and we set limits on the production cross sections of Z' bosons and RS gluons, for signal models with varying widths. For some signal models, we eclipse previous exclusion limits, excluding Z' bosons with masses up to 3.3 (3.8) TeV, for Z' relative widths of 10% (30%) of their masses. |
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Compact Muon Solenoid LHC, CERN |
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