CMS-HIN-19-001 ; CERN-EP-2020-101 | ||
Evidence for top quark production in nucleus-nucleus collisions | ||
CMS Collaboration | ||
19 June 2020 | ||
Phys. Rev. Lett. 125 (2020) 222001 | ||
Abstract: Ultrarelativistic heavy ion collisions recreate in the laboratory the thermodynamical conditions prevailing in the early universe up to 10$^{-6}$ seconds, thereby allowing the study of the quark-gluon plasma (QGP), a state of quantum chromodynamics (QCD) matter with deconfined partons. The top quark, the heaviest elementary particle known, is accessible in nucleus-nucleus collisions at the CERN LHC, and constitutes a novel probe of the QGP. Here, we report the first-ever evidence for the production of top quarks in nucleus-nucleus collisions, using lead-lead collision data at a nucleon-nucleon centre-of-mass energy of 5.02 TeV recorded by the CMS experiment. Two methods are used to measure the cross section for top quark pair production (${\sigma_{\mathrm{t\bar{t}}}} $) via the decay into charged leptons (electrons or muons) and bottom quarks. One method relies on the leptonic information alone, and the second one exploits, in addition, the presence of bottom quarks. The measured cross sections, ${\sigma_{\mathrm{t\bar{t}}}} = $ 2.54$^{+0.84}_{-0.74}$ and 2.03$^{+0.71}_{-0.64}$ $\mu$b, respectively, are compatible with expectations from scaled proton-proton data and QCD predictions. | ||
Links: e-print arXiv:2006.11110 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; |
Figures & Tables | Summary | Additional Figures | References | CMS Publications |
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Figures | |
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Figure 1:
Event display of a candidate ${\mathrm{t} \mathrm{\bar{t}}}$ event measured in PbPb collisions where each top quark decays into a bottom quark and a W boson. The b quarks and W bosons, in turn, produce jets and leptons, respectively. The event is interpreted as originating from the dilepton decay chain ${\mathrm{t} \mathrm{\bar{t}}} \to (\mathrm{b} \mathrm{W^{+}}) (\mathrm{\bar{b}} \mathrm{W^{-}}) \to (\mathrm{b} \, \mathrm{e^{+}} \nu_{\mathrm{e}}) (\mathrm{\bar{b}} \, \mu^{-} \nu_{\mu})$. |
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Figure 2:
Observed (markers) and prefit expected (filled histograms) BDT discriminator distributions in the ${\mathrm{e^{+}} \mathrm{e^{-}} }$ (left), ${\mu^{+} \mu^{-} }$ (middle), and ${\mathrm{e^{\pm}} \mu ^\mp}$ (right) final states. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of ${\mathrm{t} \mathrm{\bar{t}}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations, including the ${\mathrm{t} \mathrm{\bar{t}}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Figure 2-a:
Observed (markers) and prefit expected (filled histograms) BDT discriminator distributions in the ${\mathrm{e^{+}} \mathrm{e^{-}} }$ final state. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of ${\mathrm{t} \mathrm{\bar{t}}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the ${\mathrm{t} \mathrm{\bar{t}}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Figure 2-b:
Observed (markers) and prefit expected (filled histograms) BDT discriminator distributions in the ${\mu^{+} \mu^{-} }$ final state. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of ${\mathrm{t} \mathrm{\bar{t}}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the ${\mathrm{t} \mathrm{\bar{t}}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Figure 2-c:
Observed (markers) and prefit expected (filled histograms) BDT discriminator distributions in the ${\mathrm{e^{\pm}} \mu ^\mp}$ final state. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of ${\mathrm{t} \mathrm{\bar{t}}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the ${\mathrm{t} \mathrm{\bar{t}}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Figure 3:
Observed (markers) and postfit predicted (filled histograms) BDT discriminator distributions in the ${\mathrm{e^{+}} \mathrm{e^{-}} }$ (left), ${\mu^{+} \mu^{-} }$ (middle), and ${\mathrm{e^{\pm}} \mu ^\mp}$ (right) final states separately for the 0b-, 1b-, and 2b-tagged jet multiplicity categories. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of ${\mathrm{t} \mathrm{\bar{t}}}$ signal and backgrounds. The lower panels display the ratio of the data to predictions, including the ${\mathrm{t} \mathrm{\bar{t}}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Figure 3-a:
Observed (markers) and postfit predicted (filled histograms) BDT discriminator distributions in the ${\mathrm{e^{+}} \mathrm{e^{-}} }$ final state separately for the 0b-, 1b-, and 2b-tagged jet multiplicity categories. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of ${\mathrm{t} \mathrm{\bar{t}}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the ${\mathrm{t} \mathrm{\bar{t}}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Figure 3-b:
Observed (markers) and postfit predicted (filled histograms) BDT discriminator distributions in the ${\mu^{+} \mu^{-} }$ final state separately for the 0b-, 1b-, and 2b-tagged jet multiplicity categories. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of ${\mathrm{t} \mathrm{\bar{t}}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the ${\mathrm{t} \mathrm{\bar{t}}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Figure 3-c:
Observed (markers) and postfit predicted (filled histograms) BDT discriminator distributions in the ${\mathrm{e^{\pm}} \mu ^\mp}$ final state separately for the 0b-, 1b-, and 2b-tagged jet multiplicity categories. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of ${\mathrm{t} \mathrm{\bar{t}}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the ${\mathrm{t} \mathrm{\bar{t}}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Figure 4:
Inclusive ${\mathrm{t} \mathrm{\bar{t}}}$ cross sections measured with two methods in the combined ${\mathrm{e^{+}} \mathrm{e^{-}} }$, ${\mu^{+} \mu^{-} }$, and ${\mathrm{e^{\pm}} \mu ^\mp}$ final states in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV, and pp results at $ \sqrt {s} = $ 5.02 TeV (scaled by $A^2$) from Ref. [21]. The measurements are compared with theoretical predictions at NNLO+NNLL accuracy in QCD [37]. The inner (outer) experimental uncertainty bars include statistical (statistical and systematic, added in quadrature) uncertainties. The inner (outer) theoretical uncertainty bands correspond to nuclear [31,36] or free-nucleon [32,33] PDF (PDF and scale, added in quadrature) uncertainties. |
Tables | |
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Table 1:
Observed impact of each source of uncertainty on the signal strength $\mu $, for the dilepton-only and dilepton plus b-tagged jets methods. The total uncertainty is obtained from the covariance matrix of the fits. The values quoted are symmetrized. |
Summary |
Evidence for top quark pair ($\mathrm{t\bar{t}}$) production in nucleus-nucleus collisions is presented for the first time, using lead-lead collision data at a nucleon-nucleon centre-of-mass energy of 5.02 TeV with a total integrated luminosity of (1.7 $\pm$ 0.1) nb$^{-1}$. The measurement utilises events with at least one pair of isolated and oppositely charged leptons (electrons or muons) with large transverse momenta, and is performed twice, with and without adding the information on the number of jets "tagged'' as originating from the hadronization of bottom (b) quarks ("b-tagged jets''). The inclusive cross section (${\sigma_{\mathrm{t\bar{t}}}} $) is derived from likelihood fits to a multivariate discriminator, which includes different leptonic kinematic variables. Using the dilepton-only and dilepton plus b-tagged jets methods, we demonstrate that top quark decay products can be identified irrespective of any possible final-state interactions with the quark-gluon plasma. The measured cross sections are ${\sigma_{\mathrm{t\bar{t}}}} = $ 2.54$^{+0.84}_{-0.74}$ and 2.03$^{+0.71}_{-0.64}$ $\mu$b, respectively. These values are compatible with, though somewhat lower than, the expectations from scaled proton-proton data and perturbative quantum chromodynamics calculations. The observed (expected) significance of the $\mathrm{t\bar{t}}$ signal against the background-only hypothesis amounts to 3.8 (4.8) and 4.0 (5.8) standard deviations in the two methods. This measurement is a milestone for the heavy ion and top quark physics programs at the LHC, and demonstrates the versatility of the CMS detector to extract such a complex signal in a very intricate environment. This is just the first step in using the top quark as a novel and powerful probe of the quark-gluon plasma. |
Additional Figures | |
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Additional Figure 1:
Observed (markers) and postfit predicted (filled histograms) BDT discriminator distributions in the $\mathrm{e^{+}} \mathrm{e^{-}}$ (left), $\mu^{+} \mu^{-}$ (middle), and $\mathrm{e^{\pm}}\mu^{\mp}$ (right) final states. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 1-a:
Observed (markers) and postfit predicted (filled histograms) BDT discriminator distributions in the $\mathrm{e^{+}} \mathrm{e^{-}}$ final state. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 1-b:
Observed (markers) and postfit predicted (filled histograms) BDT discriminator distributions in the $\mu^{+} \mu^{-}$ final state. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 1-c:
Observed (markers) and postfit predicted (filled histograms) BDT discriminator distributions in the $\mathrm{e^{\pm}}\mu^{\mp}$ final state. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 2:
Observed (markers) and prefit expected (filled histograms) BDT discriminator distributions in the $\mathrm{e^{+}} \mathrm{e^{-}}$ (left), $\mu^{+} \mu^{-}$ (middle), and $\mathrm{e^{\pm}}\mu^{\mp}$ (right) final states separately for the 0b-, 1b-, and 2b-jet multiplicity categories. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 2-a:
Observed (markers) and prefit expected (filled histograms) BDT discriminator distributions in the $\mathrm{e^{+}} \mathrm{e^{-}}$ final state separately for the 0b-, 1b-, and 2b-jet multiplicity categories. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 2-b:
Observed (markers) and prefit expected (filled histograms) BDT discriminator distributions in the $\mu^{+} \mu^{-}$ final state separately for the 0b-, 1b-, and 2b-jet multiplicity categories. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 2-c:
Observed (markers) and prefit expected (filled histograms) BDT discriminator distributions in the $\mathrm{e^{\pm}}\mu^{\mp}$ final state separately for the 0b-, 1b-, and 2b-jet multiplicity categories. The data are shown with markers, and the signal and background processes with filled histograms. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 3:
Invariant mass distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$ (left), $\mu^{+} \mu^{-}$ (middle), and $\mathrm{e^{\pm}}\mu^{\mp}$ (right) channels. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 3-a:
Invariant mass distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$ channel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 3-b:
Invariant mass distributions of the lepton pairs in the $\mu^{+} \mu^{-}$ channel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 3-c:
Invariant mass distributions of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 4:
Postfit predicted multiplicity distributions of the b-tagged jets ($N_{ {b-tag}}$) in the $\mathrm{e^{+}} \mathrm{e^{-}}$ (left), $\mu^{+} \mu^{-}$ (middle), and $\mathrm{e^{\pm}}\mu^{\mp}$ (right) channels. The distribution of the Z/$\gamma ^{*}$ background is taken from the data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 4-a:
Postfit predicted multiplicity distributions of the b-tagged jets ($N_{ {b-tag}}$) in the $\mathrm{e^{+}} \mathrm{e^{-}}$ channel. The distribution of the Z/$\gamma ^{*}$ background is taken from the data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 4-b:
Postfit predicted multiplicity distributions of the b-tagged jets ($N_{ {b-tag}}$) in the $\mu^{+} \mu^{-}$ channel. The distribution of the Z/$\gamma ^{*}$ background is taken from the data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 4-c:
Postfit predicted multiplicity distributions of the b-tagged jets ($N_{ {b-tag}}$) in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel. The distribution of the Z/$\gamma ^{*}$ background is taken from the data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 5:
Transverse momentum distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$, $\mu^{+} \mu^{-}$, and $\mathrm{e^{\pm}}\mu^{\mp}$ (BDT $ > $ 0.5, left), $\mathrm{e^{+}} \mathrm{e^{-}}$ and $\mu^{+} \mu^{-}$ (middle), and $\mathrm{e^{\pm}}\mu^{\mp}$ (right) channels. In the upper (lower) row, the prefit (postfit) expectations (predictions) are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown for the postfit distributions as inset panels. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit (postfit) uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations (predictions), including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit (postfit) uncertainties in the predictions. |
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Additional Figure 5-a:
Transverse momentum distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$, $\mu^{+} \mu^{-}$, and $\mathrm{e^{\pm}}\mu^{\mp}$ (BDT $ > $ 0.5) channels. The prefit expectations are compared to data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the predictions. |
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Additional Figure 5-b:
Transverse momentum distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$ and $\mu^{+} \mu^{-}$ hannels. The prefit expectations are compared to data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the predictions. |
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Additional Figure 5-c:
Transverse momentum distributions of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channels. The prefit expectations are compared to data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the predictions. |
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Additional Figure 5-d:
Transverse momentum distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$, $\mu^{+} \mu^{-}$, and $\mathrm{e^{\pm}}\mu^{\mp}$ (BDT $ > $ 0.5) channels. The postfit predictions are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown as an inset panel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 5-e:
Transverse momentum distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$ and $\mu^{+} \mu^{-}$ hannels. The postfit predictions are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown as an inset panel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 5-f:
Transverse momentum distributions of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channels. The postfit predictions are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown as an inset panel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 6:
"Acoplanarity'', i.e. 1${-}|\Delta \phi (\ell ^+ \ell ^-)|/\pi $, distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$, $\mu^{+} \mu^{-}$, and $\mathrm{e^{\pm}}\mu^{\mp}$ (BDT $ > $ 0.5, left), $\mathrm{e^{+}} \mathrm{e^{-}}$ and $\mu^{+} \mu^{-}$ (middle), and $\mathrm{e^{\pm}}\mu^{\mp}$ (right) channels. In the upper (lower) row, the prefit (postfit) expectations (predictions) are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown for the postfit distributions as inset panels. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit (postfit) uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations (predictions), including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit (postfit) uncertainties in the predictions. |
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Additional Figure 6-a:
"Acoplanarity'', i.e. 1${-}|\Delta \phi (\ell ^+ \ell ^-)|/\pi $, distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$, $\mu^{+} \mu^{-}$, and $\mathrm{e^{\pm}}\mu^{\mp}$ (BDT $ > $ 0.5) channels. The prefit expectations are compared to data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the predictions. |
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Additional Figure 6-b:
"Acoplanarity'', i.e. 1${-}|\Delta \phi (\ell ^+ \ell ^-)|/\pi $, distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$ and $\mu^{+} \mu^{-}$ channels. The prefit expectations are compared to data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the predictions. |
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Additional Figure 6-c:
"Acoplanarity'', i.e. 1${-}|\Delta \phi (\ell ^+ \ell ^-)|/\pi $, distributions of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channels. The prefit expectations are compared to data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the predictions. |
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Additional Figure 6-d:
"Acoplanarity'', i.e. 1${-}|\Delta \phi (\ell ^+ \ell ^-)|/\pi $, distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$, $\mu^{+} \mu^{-}$, and $\mathrm{e^{\pm}}\mu^{\mp}$ (BDT $ > $ 0.5) channels. The postfit predictions are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown as an inset panel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 6-e:
"Acoplanarity'', i.e. 1${-}|\Delta \phi (\ell ^+ \ell ^-)|/\pi $, distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$ and $\mu^{+} \mu^{-}$ channels. The postfit predictions are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown as an inset panel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 6-f:
"Acoplanarity'', i.e. 1${-}|\Delta \phi (\ell ^+ \ell ^-)|/\pi $, distributions of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channels. The postfit predictions are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown as an inset panel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 7:
Sphericity distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$, $\mu^{+} \mu^{-}$, and $\mathrm{e^{\pm}}\mu^{\mp}$ (BDT $ > $ 0.5, left), $\mathrm{e^{+}} \mathrm{e^{-}}$ and $\mu^{+} \mu^{-}$ (middle), and $\mathrm{e^{\pm}}\mu^{\mp}$ (right) channels. In the upper (lower) row, the prefit (postfit) expectations (predictions) are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown for the postfit distributions as inset panels. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit (postfit) uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panels display the ratio of the data to expectations (predictions), including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit (postfit) uncertainties in the predictions. |
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Additional Figure 7-a:
Sphericity distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$, $\mu^{+} \mu^{-}$, and $\mathrm{e^{\pm}}\mu^{\mp}$ (BDT $ > $ 0.5) channel. The prefit expectations (predictions) are compared to data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the predictions. |
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Additional Figure 7-b:
Sphericity distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$ and $\mu^{+} \mu^{-}$ channel. The prefit expectations (predictions) are compared to data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the predictions. |
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Additional Figure 7-c:
Sphericity distributions of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel. The prefit expectations (predictions) are compared to data. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the prefit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the predictions. |
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Additional Figure 7-d:
Sphericity distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$, $\mu^{+} \mu^{-}$, and $\mathrm{e^{\pm}}\mu^{\mp}$ (BDT $ > $ 0.5) channel. The postfit expectations (predictions) are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown as an inset panel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
![]() png pdf |
Additional Figure 7-e:
Sphericity distributions of the lepton pairs in the $\mathrm{e^{+}} \mathrm{e^{-}}$ and $\mu^{+} \mu^{-}$ channel. The postfit expectations (predictions) are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown as an inset panel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 7-f:
Sphericity distributions of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel. The postfit expectations (predictions) are compared to data. The comparison between the $\mathrm{t\bar{t}}$ signal and the background-subtracted data is shown as an inset panel. Backgrounds and signal are shown with the filled histograms and data are shown with the markers. The vertical bars on the markers represent the statistical uncertainties in data. The hatched regions show the postfit uncertainties in the sum of $\mathrm{t\bar{t}}$ signal and backgrounds. The lower panel displays the ratio of the data to predictions, including the $\mathrm{t\bar{t}}$ signal, with bands representing the postfit uncertainties in the predictions. |
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Additional Figure 8:
Projected invariant mass (top left), transverse momentum (top right), acoplanarity (bottom left), and sphericity (bottom right) distributions of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel at High-Luminosity LHC. Backgrounds and signal are shown with the filled histograms and pseudodata are shown with the markers. The vertical bars on the markers represent the expected statistical uncertainties in pseudodata. The lower panels display the ratio of the pseudodata to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 8-a:
Projected invariant mass distribution of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel at High-Luminosity LHC. Backgrounds and signal are shown with the filled histograms and pseudodata are shown with the markers. The vertical bars on the markers represent the expected statistical uncertainties in pseudodata. The lower panel displays the ratio of the pseudodata to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 8-b:
Projected transverse momentum distribution of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel at High-Luminosity LHC. Backgrounds and signal are shown with the filled histograms and pseudodata are shown with the markers. The vertical bars on the markers represent the expected statistical uncertainties in pseudodata. The lower panel displays the ratio of the pseudodata to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 8-c:
Projected acoplanarity distribution of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel at High-Luminosity LHC. Backgrounds and signal are shown with the filled histograms and pseudodata are shown with the markers. The vertical bars on the markers represent the expected statistical uncertainties in pseudodata. The lower panel displays the ratio of the pseudodata to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
![]() png pdf |
Additional Figure 8-d:
Projected sphericity distribution of the lepton pairs in the $\mathrm{e^{\pm}}\mu^{\mp}$ channel at High-Luminosity LHC. Backgrounds and signal are shown with the filled histograms and pseudodata are shown with the markers. The vertical bars on the markers represent the expected statistical uncertainties in pseudodata. The lower panel displays the ratio of the pseudodata to expectations, including the $\mathrm{t\bar{t}}$ signal, with bands representing the prefit uncertainties in the expectations. |
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Additional Figure 9:
The measured and projected at High-Luminosity LHC inclusive $\mathrm{t\bar{t}}$ cross sections making use of the final-state dilepton kinematic properties alone, in the combined ${\mathrm{e^{+}} \mathrm{e^{-}} }$, ${\mu^{+} \mu^{-} }$, and $\mathrm{e^{\pm}}\mu^{\mp}$ final states in PbPB collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV, and pp results at $ \sqrt {s} = $ 5.02 TeV (scaled by $A^2$) from Ref. [CMS:2021gwv]. The measurements and projections are compared with theoretical predictions at NNLO+NNLL accuracy in QCD [30,37]. The inner (outer) experimental uncertainty bars include statistical (statistical and systematic, added in quadrature) uncertainties. The inner (outer) theoretical uncertainty bands correspond to nuclear [31,36] or free-nucleon [32,33] PDF (PDF and scale, added in quadrature) uncertainties. |
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Compact Muon Solenoid LHC, CERN |
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