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CMS-PAS-FTR-18-009
Search for t¯t resonances at the HL-LHC and HE-LHC with the Phase-2 CMS detector
CMS Collaboration
November 2018
Abstract: A search for a heavy resonance decaying into a t¯t pair is presented using the upgraded Phase-2 CMS detector design at the High-Luminosity LHC (HL-LHC) and High-Energy LHC (HE-LHC), with center-of-mass energies of 14 and 27 TeV, respectively, and integrated luminosities of 3 and 15 ab−1. Two distinct final states with either a single lepton or no leptons are considered. Jet substructure techniques and top quark identification algorithms are used for the object reconstruction. At the HL-LHC (HE-LHC), the production of a Randall-Sundrum gluon can be excluded at 95% confidence level with a mass up to 6.6 (10.7) TeV or can be discovered at 5σ significance with a mass up to 5.7 (9.4) TeV.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;
Figures & Tables Summary References CMS Publications
Figures

png pdf 		Figure 1:
Leading order Feynman diagrams showing pair production and decays of top quark with (left) single-lepton and (right) fully hadronic final states.

png pdf 		Figure 1-a:
Leading order Feynman diagrams showing pair production and decays of top quark with (left) single-lepton and (right) fully hadronic final states.

png pdf 		Figure 1-b:
Leading order Feynman diagrams showing pair production and decays of top quark with (left) single-lepton and (right) fully hadronic final states.

png pdf 		Figure 2:
The generated and reconstructed RSG mass distributions in the (left) single-lepton and (right) fully hadronic final states. The distributions are shown after the full event selection in each final state, as described in Sections xxxxx and yyyyy.

png pdf 		Figure 2-a:
The generated and reconstructed RSG mass distributions in the (left) single-lepton and (right) fully hadronic final states. The distributions are shown after the full event selection in each final state, as described in Sections xxxxx and yyyyy.

png pdf 		Figure 2-b:
The generated and reconstructed RSG mass distributions in the (left) single-lepton and (right) fully hadronic final states. The distributions are shown after the full event selection in each final state, as described in Sections xxxxx and yyyyy.

png pdf 		Figure 3:
The distributions of mt¯t in events with (top) zero or (bottom) one t-tagged jets for (left) single-electron or (right) single-muon samples. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 3-a:
The distributions of mt¯t in events with (top) zero or (bottom) one t-tagged jets for (left) single-electron or (right) single-muon samples. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 3-b:
The distributions of mt¯t in events with (top) zero or (bottom) one t-tagged jets for (left) single-electron or (right) single-muon samples. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 3-c:
The distributions of mt¯t in events with (top) zero or (bottom) one t-tagged jets for (left) single-electron or (right) single-muon samples. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 3-d:
The distributions of mt¯t in events with (top) zero or (bottom) one t-tagged jets for (left) single-electron or (right) single-muon samples. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 4:
The distribution of the RSG candidate mass for (left) Δy<1 or (right) Δy>1 in the (top) zero, (middle) one, or (bottom) two b-tag event categories in the fully hadronic final state. All variables presented after full selection. Along with the RSG signal, the two main backgrounds are shown: t¯t and QCD multijets. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 4-a:
The distribution of the RSG candidate mass for (left) Δy<1 or (right) Δy>1 in the (top) zero, (middle) one, or (bottom) two b-tag event categories in the fully hadronic final state. All variables presented after full selection. Along with the RSG signal, the two main backgrounds are shown: t¯t and QCD multijets. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 4-b:
The distribution of the RSG candidate mass for (left) Δy<1 or (right) Δy>1 in the (top) zero, (middle) one, or (bottom) two b-tag event categories in the fully hadronic final state. All variables presented after full selection. Along with the RSG signal, the two main backgrounds are shown: t¯t and QCD multijets. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 4-c:
The distribution of the RSG candidate mass for (left) Δy<1 or (right) Δy>1 in the (top) zero, (middle) one, or (bottom) two b-tag event categories in the fully hadronic final state. All variables presented after full selection. Along with the RSG signal, the two main backgrounds are shown: t¯t and QCD multijets. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 4-d:
The distribution of the RSG candidate mass for (left) Δy<1 or (right) Δy>1 in the (top) zero, (middle) one, or (bottom) two b-tag event categories in the fully hadronic final state. All variables presented after full selection. Along with the RSG signal, the two main backgrounds are shown: t¯t and QCD multijets. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 4-e:
The distribution of the RSG candidate mass for (left) Δy<1 or (right) Δy>1 in the (top) zero, (middle) one, or (bottom) two b-tag event categories in the fully hadronic final state. All variables presented after full selection. Along with the RSG signal, the two main backgrounds are shown: t¯t and QCD multijets. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 4-f:
The distribution of the RSG candidate mass for (left) Δy<1 or (right) Δy>1 in the (top) zero, (middle) one, or (bottom) two b-tag event categories in the fully hadronic final state. All variables presented after full selection. Along with the RSG signal, the two main backgrounds are shown: t¯t and QCD multijets. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 5:
Distributions of mt¯t in events with (top) zero or (bttom) one t-tagged jets for (left) the single-electron or (right) single-muon final state. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 5-a:
Distributions of mt¯t in events with (top) zero or (bttom) one t-tagged jets for (left) the single-electron or (right) single-muon final state. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 5-b:
Distributions of mt¯t in events with (top) zero or (bttom) one t-tagged jets for (left) the single-electron or (right) single-muon final state. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 5-c:
Distributions of mt¯t in events with (top) zero or (bttom) one t-tagged jets for (left) the single-electron or (right) single-muon final state. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 5-d:
Distributions of mt¯t in events with (top) zero or (bttom) one t-tagged jets for (left) the single-electron or (right) single-muon final state. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 6:
Distributions of mt¯t for (top left) zero, (top right) one, or (bottom) two b tag event categories in the fully hadronic final state. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 6-a:
Distributions of mt¯t for (top left) zero, (top right) one, or (bottom) two b tag event categories in the fully hadronic final state. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 6-b:
Distributions of mt¯t for (top left) zero, (top right) one, or (bottom) two b tag event categories in the fully hadronic final state. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 6-c:
Distributions of mt¯t for (top left) zero, (top right) one, or (bottom) two b tag event categories in the fully hadronic final state. The statistical uncertainties are scaled down by the square root of the projected luminosity. Variable sized bins are used for each category so that the statistical uncertainty on the total background in each bin is less than 10%. The bin contents of the distributions are divided by their bin width. The overflow events are added to the last bin and its content is also divided by the width of the last bin.

png pdf 		Figure 7:
95% CL expected upper limits (left) and 3σ and 5σ discovery reaches (right) for an RSG decaying to t¯t at 300 fb−1 (top) and 3 ab−1 (bottom) for the combined single-lepton and fully hadronic final states. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 7-a:
95% CL expected upper limits (left) and 3σ and 5σ discovery reaches (right) for an RSG decaying to t¯t at 300 fb−1 (top) and 3 ab−1 (bottom) for the combined single-lepton and fully hadronic final states. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 7-b:
95% CL expected upper limits (left) and 3σ and 5σ discovery reaches (right) for an RSG decaying to t¯t at 300 fb−1 (top) and 3 ab−1 (bottom) for the combined single-lepton and fully hadronic final states. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 7-c:
95% CL expected upper limits (left) and 3σ and 5σ discovery reaches (right) for an RSG decaying to t¯t at 300 fb−1 (top) and 3 ab−1 (bottom) for the combined single-lepton and fully hadronic final states. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 7-d:
95% CL expected upper limits (left) and 3σ and 5σ discovery reaches (right) for an RSG decaying to t¯t at 300 fb−1 (top) and 3 ab−1 (bottom) for the combined single-lepton and fully hadronic final states. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 8:
95% CL expected cross section limits for 3 ab−1 projection. Comparisons of the contributions from each final state to the combination is shown on the left. The effect of different systematic uncertainty scenarios on the combined limits is shown on the right. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 8-a:
95% CL expected cross section limits for 3 ab−1 projection. Comparisons of the contributions from each final state to the combination is shown on the left. The effect of different systematic uncertainty scenarios on the combined limits is shown on the right. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 8-b:
95% CL expected cross section limits for 3 ab−1 projection. Comparisons of the contributions from each final state to the combination is shown on the left. The effect of different systematic uncertainty scenarios on the combined limits is shown on the right. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 9:
95% CL expected upper limits (left) and 3σ and 5σ discovery potential (right) for an RSG decaying to t¯t with 15 ab−1 from the HE-LHC for the combined single-lepton and fully hadronic final states. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 9-a:
95% CL expected upper limits (left) and 3σ and 5σ discovery potential (right) for an RSG decaying to t¯t with 15 ab−1 from the HE-LHC for the combined single-lepton and fully hadronic final states. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf 		Figure 9-b:
95% CL expected upper limits (left) and 3σ and 5σ discovery potential (right) for an RSG decaying to t¯t with 15 ab−1 from the HE-LHC for the combined single-lepton and fully hadronic final states. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].
Tables

png pdf
 Table 1:
Summary of the selection efficiencies for the two final states for the signal hypotheses considered.

png pdf
 Table 2:
Summary of the sources of systematic uncertainties.

png pdf
 Table 3:
Expected cross section limits at 95% CL and discovery reaches at 3 and 5σ in the combined single-lepton and fully hadronic final states for an RSG decaying to t¯t. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].

png pdf
 Table 4:
Expected cross section limits at 95% CL and discovery potential at 3σ and 5σ in the combined single-lepton and fully hadronic final states for an RSG decaying to t¯t with 15 ab−1 from the HE-LHC. The LO signal theory cross sections are scaled to NLO using a k factor of 1.3 [44].
Summary
We have presented a sensitivity projection for heavy resonant tˉt pair production using the upgraded Phase-2 CMS detector design at the High-Luminosity LHC (HL-LHC) and High-Energy LHC (HE-LHC), with center-of-mass energies of 14 and 27 TeV and integrated luminosities of 3 and 15 ab−1. Two distinct final states, single-lepton or fully hadronic, are considered. We set limits on the production cross sections of a Randall-Sundrum gluon and exclude masses up to 6.6 (10.7) TeV at 95% confidence level at the HL-LHC (HE-LHC). The Randall-Sundrum gluon with a mass up to 5.7 (9.4) TeV can be discovered with 5σ significance at the HL-LHC (HE-LHC).
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