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| CMS-PAS-EXO-21-019 | ||
| A search for pair production of leptoquarks decaying to muons and bottom quarks at $ \sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| 21 August 2023 | ||
| Abstract: A search for pair production of leptoquarks each decaying to a muon and a b quark is performed using proton-proton collision data collected at $ \sqrt{s}= $ 13 TeV in 2016-2018 with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. Scalar leptoquarks with masses less than 1810 GeV are excluded, assuming a 100% branching fraction of the leptoquark to a muon and a b quark. These limits represent the most stringent limits to date on leptoquarks decaying to muons and b quarks. | ||
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Links:
CDS record (PDF) ;
Physics Briefing ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to PRD. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Dominant leading-order Feynman diagrams for pair production of LQs at the LHC. |
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Figure 1-a:
Dominant leading-order Feynman diagrams for pair production of LQs at the LHC. |
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Figure 1-b:
Dominant leading-order Feynman diagrams for pair production of LQs at the LHC. |
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Figure 1-c:
Dominant leading-order Feynman diagrams for pair production of LQs at the LHC. |
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Figure 1-d:
Dominant leading-order Feynman diagrams for pair production of LQs at the LHC. |
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Figure 2:
Comparison of data and background $ m_{\mu\mu} $ distribution at the preselection level for the $ \mathrm{Z}/\gamma^*\mathrm{+jets} $ + $ \mathrm{t} \overline{\mathrm{t}} $ +jets (left) and diboson + $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{V} $ (right) background control regions. The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 2-a:
Comparison of data and background $ m_{\mu\mu} $ distribution at the preselection level for the $ \mathrm{Z}/\gamma^*\mathrm{+jets} $ + $ \mathrm{t} \overline{\mathrm{t}} $ +jets (left) and diboson + $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{V} $ (right) background control regions. The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 2-b:
Comparison of data and background $ m_{\mu\mu} $ distribution at the preselection level for the $ \mathrm{Z}/\gamma^*\mathrm{+jets} $ + $ \mathrm{t} \overline{\mathrm{t}} $ +jets (left) and diboson + $ {\mathrm{t}\overline{\mathrm{t}}} \mathrm{V} $ (right) background control regions. The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 3:
Comparison of data and background $ p_{\mathrm{T}} $ distribution at the preselection level for the leading two muons and jets. The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 3-a:
Comparison of data and background $ p_{\mathrm{T}} $ distribution at the preselection level for the leading two muons and jets. The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 3-b:
Comparison of data and background $ p_{\mathrm{T}} $ distribution at the preselection level for the leading two muons and jets. The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 3-c:
Comparison of data and background $ p_{\mathrm{T}} $ distribution at the preselection level for the leading two muons and jets. The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 3-d:
Comparison of data and background $ p_{\mathrm{T}} $ distribution at the preselection level for the leading two muons and jets. The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 4:
Comparison of data and background BDT discriminant distributions at preselection for LQ mass hypotheses of 1500 GeV (left), 1800 GeV (middle), and 2000 GeV (right).The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 4-a:
Comparison of data and background BDT discriminant distributions at preselection for LQ mass hypotheses of 1500 GeV (left), 1800 GeV (middle), and 2000 GeV (right).The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 4-b:
Comparison of data and background BDT discriminant distributions at preselection for LQ mass hypotheses of 1500 GeV (left), 1800 GeV (middle), and 2000 GeV (right).The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 4-c:
Comparison of data and background BDT discriminant distributions at preselection for LQ mass hypotheses of 1500 GeV (left), 1800 GeV (middle), and 2000 GeV (right).The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 5:
Data and background event yields after final selections, for each scalar $ m_{\mathrm{LQ}} $ hypothesis. Each bin on the $ x $ axis represents an independent $ m_{\mathrm{LQ}} $ category, for example the first bin is a comparison of the yields after final selection in the $ m_{\mathrm{LQ}} = $ 300 GeV signal mass hypothesis, and so on. The shaded band represents the combined statistical and systematic uncertainty in the full background estimate. |
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Figure 6:
The expected and observed upper limits at 95% CL on the product of the scalar LQ pair production cross section and the branching fractions $ \beta^2 $ as a function of $ m_{\mathrm{LQ}} $. The solid lines represent the observed limits, the dashed lines represent the median expected limits, and the inner dark-green and outer light-yellow bands represent the 68% and 95% CL intervals. The $ \sigma_{\text{theory}} $ curves and their blue bands represent the theoretical scalar LQ pair production cross sections and the uncertainties on the cross sections due to the PDF prediction and renormalization and factorization scales, respectively. |
| Tables | |
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Table 1:
Systematic uncertainties in combined 2016, 2017, and 2018 signal acceptance and background yields, shown as a range over all final selections (second and third columns) as well as for the $ m_{\mathrm{LQ}} = $ 1800 GeV point (rightmost two columns). The bottom two lines show the total systematic uncertainty and the total statistical uncertainty in the simulated samples, respectively. |
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Table 2:
Event yields in combined 2016, 2017, and 2018 data at the final selection level. Uncertainties are statistical unless otherwise indicated. |
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Table 3:
Total signal selection efficiency, defined as events passing final selection divided by number of generated events. Uncertainties are statistical. |
| Summary |
| A search has been presented for pair production of leptoquarks decaying to muons and bottom quarks using proton-proton collision data collected at $ \sqrt{s} = $ 13 TeV in 2016--2018 with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb$ ^{-1} $. Limits are set at 95% confidence level on the product of the scalar leptoquark pair production cross section and $ \beta^2 $, as a function of the leptoquark mass $ m_{\mathrm{LQ}} $, where $ \beta $ is the branching fraction of the leptoquark to decay to a muon and a bottom quark. Leptoquarks with masses less than 1810 GeV are excluded for $ \beta= $ 1.0. This represents the most stringent limits to date on these models. |
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