CMS-PAS-B2G-17-008 | ||
Search for top quark partners with charge 5/3 in the single-lepton final state at $\sqrt{s}= $ 13 TeV | ||
CMS Collaboration | ||
May 2017 | ||
Abstract: A search for the pair production of heavy partners of the top quark with an exotic electric charge 5/3 ($X_{5/3}$) decaying into a W boson and a top quark is presented. The search uses data collected in 2016 in proton-proton collisions at a center-of-mass energy of 13 TeV with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Final states considered include one electron or muon, missing transverse energy, and four or more jets. The $X_{5/3}$ masses with right-handed (left-handed) couplings below 1.32 (1.30) TeV are excluded at 95% confidence level. | ||
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; |
Figures | |
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Figure 1:
Leading order Feynman diagrams for the production and decay of pairs of $X_{5/3}$ particles. |
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Figure 1-a:
Leading order Feynman diagram for the production and decay of pairs of $X_{5/3}$ particles. |
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Figure 1-b:
Leading order Feynman diagram for the production and decay of pairs of $X_{5/3}$ particles. |
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Figure 2:
Distributions of min [M($\ell $, b)] (left) and $\Delta R$($\ell $, $j_{2}$) (right) in data and simulation for selected events with at least three jets and leading AK4 jet $ {p_{\mathrm {T}}} > $ 250 GeV. The events in the overflow bin are added to the last bin of the distributions. The bottom panel on all plots shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. The signal cross sections are scaled by a factor of 120 (80) on the min [M($\ell $, b)] ($\Delta R$($\ell $, $j_{2}$)) distributions in order to make the shape differences between signal and background visible. |
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Figure 2-a:
Distribution of min [M($\ell $, b)] in data and simulation for selected events with at least three jets and leading AK4 jet $ {p_{\mathrm {T}}} > $ 250 GeV. The events in the overflow bin are added to the last bin of the distribution. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. The signal cross sections are scaled by a factor of 120 on the min [M($\ell $, b)] distribution in order to make the shape difference between signal and background visible. |
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Figure 2-b:
Distribution of $\Delta R$($\ell $, $j_{2}$) in data and simulation for selected events with at least three jets and leading AK4 jet $ {p_{\mathrm {T}}} > $ 250 GeV. The events in the overflow bin are added to the last bin of the distribution. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. The signal cross sections are scaled by a factor of 80 on the $\Delta R$($\ell $, $j_{2}$) distribution in order to make the shape difference between signal and background visible. |
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Figure 3:
Distributions of min [M($\ell $, b)] in events with 0 t-tagged jet, (top) 0 or (bottom) $\ge $1 W-tagged jets and (left) 1 or (right) $\ge $2 b-tagged jets for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distributions. The distributions are given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel on all plots shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 3-a:
Distribution of min [M($\ell $, b)] in events with 0 t-tagged jet, $\ge $1 W-tagged jets, $\ge $2 b-tagged jets, for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distribution. The distribution is given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 3-b:
Distributions of min [M($\ell $, b)] in events with 0 t-tagged jet, (top) 0 or (bottom) $\ge $1 W-tagged jets and (left) 1 or (right) $\ge $2 b-tagged jets for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distributions. The distributions are given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel on all plots shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 3-c:
Distributions of min [M($\ell $, b)] in events with 0 t-tagged jet, (top) 0 or (bottom) $\ge $1 W-tagged jets and (left) 1 or (right) $\ge $2 b-tagged jets for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distributions. The distributions are given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel on all plots shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 3-d:
Distributions of min [M($\ell $, b)] in events with 0 t-tagged jet, (top) 0 or (bottom) $\ge $1 W-tagged jets and (left) 1 or (right) $\ge $2 b-tagged jets for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distributions. The distributions are given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel on all plots shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 4:
Distributions of min [M($\ell $, b)] in events with $\ge $1 t-tagged jet, (top) 0 or (bottom) $\ge $1 W-tagged jets and (left) 1 or (right) $\ge $2 b-tagged jets for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distributions. The distributions are given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel on all plots shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 4-a:
Distribution of min [M($\ell $, b)] in events with $\ge $1 t-tagged jet, 0 W-tagged jet, 1 b-tagged jet, for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distribution. The distribution is given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 4-b:
Distribution of min [M($\ell $, b)] in events with $\ge $1 t-tagged jet, 0 W-tagged jet, $\ge $2 b-tagged jets, for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distribution. The distribution is given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 4-c:
Distribution of min [M($\ell $, b)] in events with $\ge $1 t-tagged jet, $\ge $1 W-tagged jets, 1 b-tagged jet, for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distribution. The distribution is given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 4-d:
Distribution of min [M($\ell $, b)] in events with $\ge $1 t-tagged jet, $\ge $1 W-tagged jets, $\ge $2 b-tagged jets, for combined electron and muon samples in the signal region. The events in the overflow bin are added to the last bin of the distribution. The distribution is given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than 30%. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 5:
Distributions of min [M($\ell $, b)] in the ${\mathrm{ t } {}\mathrm{ \bar{t} } } $ control region, for 1 b-tagged jet (top left) and $\ge $2 b-tagged jets (top right) categories, and of min [M($\ell $, jets)] in the W + jets control region, for 0 W-tagged (bottom left) and $\ge $1 W-tagged jet (bottom right) categories. Electron and muon event samples are combined. The events in the overflow bin are added to the last bin of the distributions. The distributions are given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than $30%$. The bottom panel on all plots shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 5-a:
Distribution of min [M($\ell $, b)] in the ${\mathrm{ t } {}\mathrm{ \bar{t} } } $ control region, for the 1 b-tagged jet category. Electron and muon event samples are combined. The events in the overflow bin are added to the last bin of the distribution. The distribution is given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than $30%$. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 5-b:
Distribution of min [M($\ell $, b)] in the ${\mathrm{ t } {}\mathrm{ \bar{t} } } $ control region, for the $\ge $2 b-tagged jets category. Electron and muon event samples are combined. The events in the overflow bin are added to the last bin of the distribution. The distribution is given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than $30%$. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 5-c:
Distribution of min [M($\ell $, jets)] in the W + jets control region, for 0 W-tagged category. Electron and muon event samples are combined. The events in the overflow bin are added to the last bin of the distribution. The distribution is given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than $30%$. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 5-d:
Distribution of min [M($\ell $, jets)] in the W + jets control region, for $\ge $1 W-tagged jet category. Electron and muon event samples are combined. The events in the overflow bin are added to the last bin of the distribution. The distribution is given variable sized bins in each category so that the statistical uncertainty on the total background in each bin is less than $30%$. The bottom panel shows the difference between the observed and the predicted number of events in that bin divided by the total uncertainty ($\sigma $). The total uncertainty is calculated as the sum in quadrature of the statistical uncertainty on the observed measurement and statistical and systematic uncertainties on the background. |
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Figure 6:
95% CL expected and observed limits for a left-handed (left) and right-handed (right) $X_{5/3}$ after combining all categories. The theoretical uncertainty on the signal cross section is shown with a band around the theoretical prediction. |
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Figure 6-a:
95% CL expected and observed limits for a left-handed $X_{5/3}$ after combining all categories. The theoretical uncertainty on the signal cross section is shown with a band around the theoretical prediction. |
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Figure 6-b:
95% CL expected and observed limits for a right-handed $X_{5/3}$ after combining all categories. The theoretical uncertainty on the signal cross section is shown with a band around the theoretical prediction. |
Tables | |
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Table 1:
Expected (observed) number of background (data) events passing the final selection requirements, in the signal region ($\Delta R$($\ell $, $j_{2}$) $>1.0$) categories after combining electron and muon channels, with an integrated luminosity of 35.9 fb$^{-1}$. Also shown are the number of expected events for a LH 900 GeV and a RH 1.2 TeV $X_{5/3}$ signals. Uncertainties quoted in the table include both statistical and systematic contributions as listed in Table {tab:sys-error}. |
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Table 2:
Expected (observed) number of background (data) events passing the final selection requirements, in the ${\mathrm{ t } {}\mathrm{ \bar{t} } } $ and W+jets control region ($0.4<\Delta R$($\ell $, $j_{2}$) $<1.0$) categories after combining electron and muon channels, with an integrated luminosity of 35.9fb$^{-1}$. Also shown are the number of expected events for a LH 900 GeV and a RH 1.2 TeV $X_{5/3}$ signals. Uncertainties quoted in the table include both statistical and systematic contributions as listed in Table {tab:sys-error}. |
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Table 3:
Summary of systematic uncertainties with pre-fit uncertainty ranges. The systematics that affect all the background processes are indicated with "All''. |
Summary |
A search for the pair production of heavy partners of the top quark with an exotic charge 5/3 decaying into a W boson and a top quark is presented. The search uses data collected in 2016 in proton-proton collisions at a center-of-mass energy of 13 TeV with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Final states considered include an electron or a muon, missing transverse energy, and four or more jets. $X_{5/3}$ masses with right-handed (left-handed) couplings below 1.32 (1.30) TeV are excluded at 95% confidence level. |
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