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| CMS-PAS-TOP-21-004 | ||
| Measurement of the inclusive and differential $\mathrm{t\bar{t}}\gamma$ cross section and EFT interpretation in the dilepton channel at $\sqrt{s}=$ 13 TeV | ||
| CMS Collaboration | ||
| September 2021 | ||
| Abstract: The production cross section of a top quark pair in association with a photon is measured in pp collisions in the decay channel with two oppositely charged leptons ($\text{e}^\pm\mu^\mp$, $\text{e}^+\text{e}^-$, $\mu^+\mu^-$). The data set of 138 fb$^{-1}$ was recorded by the CMS experiment at $\sqrt{s}=$ 13 TeV during the 2016 to 2018 data-taking period of the CERN LHC. A fiducial phase space is defined such that photons radiated by initial-state particles, top quarks, or any of their decay products are included. An inclusive cross section of 174.4 $\pm$ 2.5 (stat) $\pm$ 6.1 (syst) fb is measured in a signal region with at least one b-tagged jet and exactly one photon with transverse momentum above 20 GeV. Differential cross sections are measured as a function of several kinematic observables of the photon, leptons, and jet, and compared to standard model predictions. The measurements are also interpreted in the standard model effective field theory framework, and limits on the relevant Wilson coefficients are combined with a previous CMS measurement of the same production process using single-lepton events. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to JHEP. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Leading-order Feynman diagrams for ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production with two leptons in the final state, where the photon is radiated by a top quark (left), by an incoming quark (middle), and by one of the charged decay products of a top quark (right). |
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Figure 1-a:
Leading-order Feynman diagrams for ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production with two leptons in the final state, where the photon is radiated by a top quark (left), by an incoming quark (middle), and by one of the charged decay products of a top quark (right). |
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Figure 1-b:
Leading-order Feynman diagrams for ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production with two leptons in the final state, where the photon is radiated by a top quark (left), by an incoming quark (middle), and by one of the charged decay products of a top quark (right). |
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Figure 1-c:
Leading-order Feynman diagrams for ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production with two leptons in the final state, where the photon is radiated by a top quark (left), by an incoming quark (middle), and by one of the charged decay products of a top quark (right). |
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Figure 2:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the number of jets (upper left) and b-tagged jets (upper right), and of the ${p_{\mathrm {T}}}$ (lower left) and $ {| \eta |}$ (lower right) of the photon, after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 2-a:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the number of jets (upper left) and b-tagged jets (upper right), and of the ${p_{\mathrm {T}}}$ (lower left) and $ {| \eta |}$ (lower right) of the photon, after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 2-b:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the number of jets (upper left) and b-tagged jets (upper right), and of the ${p_{\mathrm {T}}}$ (lower left) and $ {| \eta |}$ (lower right) of the photon, after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 2-c:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the number of jets (upper left) and b-tagged jets (upper right), and of the ${p_{\mathrm {T}}}$ (lower left) and $ {| \eta |}$ (lower right) of the photon, after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 2-d:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the number of jets (upper left) and b-tagged jets (upper right), and of the ${p_{\mathrm {T}}}$ (lower left) and $ {| \eta |}$ (lower right) of the photon, after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 3:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the scalar ${p_{\mathrm {T}}}$ sum (upper left) and the $\phi $ difference (upper right) of the two leptons, and of the ${\Delta R}$ between the photon and the closest jet (lower left) or the closest lepton (lower right), after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 3-a:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the scalar ${p_{\mathrm {T}}}$ sum (upper left) and the $\phi $ difference (upper right) of the two leptons, and of the ${\Delta R}$ between the photon and the closest jet (lower left) or the closest lepton (lower right), after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 3-b:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the scalar ${p_{\mathrm {T}}}$ sum (upper left) and the $\phi $ difference (upper right) of the two leptons, and of the ${\Delta R}$ between the photon and the closest jet (lower left) or the closest lepton (lower right), after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 3-c:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the scalar ${p_{\mathrm {T}}}$ sum (upper left) and the $\phi $ difference (upper right) of the two leptons, and of the ${\Delta R}$ between the photon and the closest jet (lower left) or the closest lepton (lower right), after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 3-d:
The observed (points) and the predicted (shaded histograms) signal and background yields as a function of the scalar ${p_{\mathrm {T}}}$ sum (upper left) and the $\phi $ difference (upper right) of the two leptons, and of the ${\Delta R}$ between the photon and the closest jet (lower left) or the closest lepton (lower right), after applying the signal selection. Distributions are shown with all relevant corrections applied, but without scaling of the signal in accordance with the inclusive fit results. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the overall sum of the predictions. |
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Figure 4:
The observed (points) and predicted (shaded histograms) event yields as a function of ${m(\ell \ell \gamma)}$ (upper left), ${m(\ell \ell)}$ (upper right), photon ${p_{\mathrm {T}}}$ (lower left), and the number of jets and b-tagged jets (lower right), after applying the event selection for the ${\mathrm{Z} \gamma}$ control region. The vertical lines on the points show the statistical uncertainties in the data, and the band the total uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the predictions. |
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Figure 4-a:
The observed (points) and predicted (shaded histograms) event yields as a function of ${m(\ell \ell \gamma)}$ (upper left), ${m(\ell \ell)}$ (upper right), photon ${p_{\mathrm {T}}}$ (lower left), and the number of jets and b-tagged jets (lower right), after applying the event selection for the ${\mathrm{Z} \gamma}$ control region. The vertical lines on the points show the statistical uncertainties in the data, and the band the total uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the predictions. |
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Figure 4-b:
The observed (points) and predicted (shaded histograms) event yields as a function of ${m(\ell \ell \gamma)}$ (upper left), ${m(\ell \ell)}$ (upper right), photon ${p_{\mathrm {T}}}$ (lower left), and the number of jets and b-tagged jets (lower right), after applying the event selection for the ${\mathrm{Z} \gamma}$ control region. The vertical lines on the points show the statistical uncertainties in the data, and the band the total uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the predictions. |
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Figure 4-c:
The observed (points) and predicted (shaded histograms) event yields as a function of ${m(\ell \ell \gamma)}$ (upper left), ${m(\ell \ell)}$ (upper right), photon ${p_{\mathrm {T}}}$ (lower left), and the number of jets and b-tagged jets (lower right), after applying the event selection for the ${\mathrm{Z} \gamma}$ control region. The vertical lines on the points show the statistical uncertainties in the data, and the band the total uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the predictions. |
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Figure 4-d:
The observed (points) and predicted (shaded histograms) event yields as a function of ${m(\ell \ell \gamma)}$ (upper left), ${m(\ell \ell)}$ (upper right), photon ${p_{\mathrm {T}}}$ (lower left), and the number of jets and b-tagged jets (lower right), after applying the event selection for the ${\mathrm{Z} \gamma}$ control region. The vertical lines on the points show the statistical uncertainties in the data, and the band the total uncertainty in the predictions. The lower panels show the ratio of the event yields in data to the predictions. |
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Figure 5:
Event yields in the signal region predicted from a simulated ${\mathrm{t} \mathrm{\bar{t}}}$ event sample (shaded histogram) and estimated from applying the transfer factor to the event yields of the same sample in the sideband region (points), as a function of the lepton flavour (left) and the photon ${p_{\mathrm {T}}}$ (right). The vertical lines on the points show the statistical uncertainties from the simulated event samples, and the band the total systematic uncertainty assigned to the nonprompt photon background estimate. The lower panels show the ratio between the two predictions. |
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Figure 5-a:
Event yields in the signal region predicted from a simulated ${\mathrm{t} \mathrm{\bar{t}}}$ event sample (shaded histogram) and estimated from applying the transfer factor to the event yields of the same sample in the sideband region (points), as a function of the lepton flavour (left) and the photon ${p_{\mathrm {T}}}$ (right). The vertical lines on the points show the statistical uncertainties from the simulated event samples, and the band the total systematic uncertainty assigned to the nonprompt photon background estimate. The lower panels show the ratio between the two predictions. |
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Figure 5-b:
Event yields in the signal region predicted from a simulated ${\mathrm{t} \mathrm{\bar{t}}}$ event sample (shaded histogram) and estimated from applying the transfer factor to the event yields of the same sample in the sideband region (points), as a function of the lepton flavour (left) and the photon ${p_{\mathrm {T}}}$ (right). The vertical lines on the points show the statistical uncertainties from the simulated event samples, and the band the total systematic uncertainty assigned to the nonprompt photon background estimate. The lower panels show the ratio between the two predictions. |
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Figure 6:
The observed (points) and predicted (shaded histograms) event yields as a function of the reconstructed photon ${p_{\mathrm {T}}}$ after applying the signal selection, for the ${\mu^{+} \mu^{-}}$ (upper left),$ {\mathrm{e^{\pm}} {\mu ^\mp}}$ (upper right), and ${\mathrm{e^{+}} \mathrm{e^{-}}}$ (lower) channels, after the values of the normalizations and nuisance parameters obtained in the fit are applied. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels of each plot show the ratio of the event yields in data to the predictions. |
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Figure 6-a:
The observed (points) and predicted (shaded histograms) event yields as a function of the reconstructed photon ${p_{\mathrm {T}}}$ after applying the signal selection, for the ${\mu^{+} \mu^{-}}$ (upper left),$ {\mathrm{e^{\pm}} {\mu ^\mp}}$ (upper right), and ${\mathrm{e^{+}} \mathrm{e^{-}}}$ (lower) channels, after the values of the normalizations and nuisance parameters obtained in the fit are applied. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels of each plot show the ratio of the event yields in data to the predictions. |
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Figure 6-b:
The observed (points) and predicted (shaded histograms) event yields as a function of the reconstructed photon ${p_{\mathrm {T}}}$ after applying the signal selection, for the ${\mu^{+} \mu^{-}}$ (upper left),$ {\mathrm{e^{\pm}} {\mu ^\mp}}$ (upper right), and ${\mathrm{e^{+}} \mathrm{e^{-}}}$ (lower) channels, after the values of the normalizations and nuisance parameters obtained in the fit are applied. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels of each plot show the ratio of the event yields in data to the predictions. |
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Figure 6-c:
The observed (points) and predicted (shaded histograms) event yields as a function of the reconstructed photon ${p_{\mathrm {T}}}$ after applying the signal selection, for the ${\mu^{+} \mu^{-}}$ (upper left),$ {\mathrm{e^{\pm}} {\mu ^\mp}}$ (upper right), and ${\mathrm{e^{+}} \mathrm{e^{-}}}$ (lower) channels, after the values of the normalizations and nuisance parameters obtained in the fit are applied. The vertical bars on the points show the statistical uncertainties in the data, and the band the systematic uncertainty in the predictions. The lower panels of each plot show the ratio of the event yields in data to the predictions. |
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Figure 7:
Fiducial ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross section in the dilepton final state measured for different lepton flavour channels, and the combined result, compared to the SM prediction at NLO accuracy. The shaded band shows the uncertainty in the prediction. |
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Figure 8:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ (lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 8-a:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ (lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 8-b:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ (lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 8-c:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ (lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 8-d:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ (lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 8-e:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ (lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 8-f:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ (lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 9:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 9-a:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 9-b:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 9-c:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 9-d:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 9-e:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
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Figure 9-f:
Absolute differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 10:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 10-a:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 10-b:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 10-c:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 10-d:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 10-e:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 10-f:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{p_{\mathrm {T}}} (\gamma)}$ (upper left), ${{| \eta |}(\gamma)}$ (upper right), ${{\Delta R} (\gamma,\ell)}$ (middle left), ${{\Delta R} (\gamma,\ell _1)}$ (middle right), ${{\Delta R} (\gamma,\ell _2)}$ lower left), and ${{\Delta R} (\gamma,b)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 11:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 11-a:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 11-b:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 11-c:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 11-d:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 11-e:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 11-f:
Normalized differential ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ production cross sections as a function of ${{\Delta R} (\ell,j)}$ (upper left), ${{| {\Delta \eta} (\ell \ell) |}}$ (upper right), ${{\Delta \varphi} (\ell \ell)}$ (middle left), ${{p_{\mathrm {T}}} (\ell \ell)}$ (middle right), ${{p_{\mathrm {T}}} (\ell _1)+ {p_{\mathrm {T}}} (\ell _2)}$ (lower left), and ${{p_{\mathrm {T}}} (j_1)}$ (lower right), as defined in Table xxxxx. The data are represented by points, with inner (outer) vertical bars indicating the statistical (total) uncertainties. The predictions obtained with the MadGraph 5\_aMC@NLO event generator interfaced with different parton shower simulations, as described in the text, are shown as horizontal lines. The theoretical uncertainties in the prediction using PYTHIA 8 are indicated by shaded bands. The lower panels display the ratios of the predictions to the measurement. The values of the ${\chi ^2}$ divided by the number of degrees of freedom (dof) quantifying the agreement between the measurement and the PYTHIA 8 prediction are indicated in the legends. |
png pdf |
Figure 12:
Expected (black) and observed (red) results from the one-dimensional scans of the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ (left) and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ (right) from the interpretation of this result. In the scans, the other Wilson coefficient is set to zero. The green (yellow) bands indicate the 68% (95%) CL contours of the Wilson coefficients. |
png pdf |
Figure 12-a:
Expected (black) and observed (red) results from the one-dimensional scans of the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ (left) and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ (right) from the interpretation of this result. In the scans, the other Wilson coefficient is set to zero. The green (yellow) bands indicate the 68% (95%) CL contours of the Wilson coefficients. |
png pdf |
Figure 12-b:
Expected (black) and observed (red) results from the one-dimensional scans of the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ (left) and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ (right) from the interpretation of this result. In the scans, the other Wilson coefficient is set to zero. The green (yellow) bands indicate the 68% (95%) CL contours of the Wilson coefficients. |
png pdf |
Figure 13:
Observed result from the two-dimensional scan of the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ from the interpretation of this result. The shading quantified by the colour scale on the right reflects the negative log-likelihood ratio with respect to the best fit value that is indicated by the star. The 68% (dashed) and 95% (solid) CL contours are shown with red (black) lines for the observed (expected) result. The triangle indicates the SM prediction. |
png pdf |
Figure 14:
Expected (black) and observed (red) results from the one-dimensional scans of the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ (left) and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ (right) from the combined interpretation of this result and the lepton+jets result from Ref. [7]. In the scans, the other Wilson coefficient is set to zero. The green (yellow) bands indicate the 68% (95%) CL contours of the Wilson coefficients. |
png pdf |
Figure 14-a:
Expected (black) and observed (red) results from the one-dimensional scans of the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ (left) and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ (right) from the combined interpretation of this result and the lepton+jets result from Ref. [7]. In the scans, the other Wilson coefficient is set to zero. The green (yellow) bands indicate the 68% (95%) CL contours of the Wilson coefficients. |
png pdf |
Figure 14-b:
Expected (black) and observed (red) results from the one-dimensional scans of the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ (left) and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ (right) from the combined interpretation of this result and the lepton+jets result from Ref. [7]. In the scans, the other Wilson coefficient is set to zero. The green (yellow) bands indicate the 68% (95%) CL contours of the Wilson coefficients. |
png pdf |
Figure 15:
Observed result from the two-dimensional scan of the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ from the combined interpretation of this result and the lepton+jets result from Ref. [7]. The shading quantified by the colour scale on the right reflects the negative log-likelihood ratio with respect to the best fit value that is indicated by the star. The 68% (dashed) and 95% (solid) CL contours are shown with red (black) lines for the observed (expected) result. The triangle indicates the SM prediction. |
| Tables | |
png pdf |
Table 1:
MC event generators used to simulate events for the signal and background processes. For each simulated process, the order of the cross section normalization calculation, the MC event generator used, and the perturbative order in QCD of the generator calculation are shown. The order is given as LO, NLO, next-to-next-to-leading order (NNLO), and including next-to-next-to-leading-logarithmic (NNLL) corrections. The symbol V refers to W and Z bosons. |
png pdf |
Table 2:
Summary of the fiducial region definition for the various objects at particle level. The "isolated'' definition for the photon requires no stable particle (except neutrinos) with $ {p_{\mathrm {T}}} > $ 5 GeV within a cone of $ {\Delta R} =$ 0.1. The parameters ${N_{\ell}}$, ${N_{\gamma}}$, and ${N_{\mathrm{b}}}$ represent the number of leptons, photons, and b jets, respectively, in the event. |
png pdf |
Table 3:
Summary of the sources of statistical and systematic uncertainties in the ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ cross section measurements. The first column lists the source of the uncertainty. The second column indicates the treatment of correlations between the uncertainties in the three years of data taking, where v means fully correlated, ${\sim}$ means partially correlated, and ${\times}$ means uncorrelated. For each systematic source, the uncertainty before applying the fit is estimated from a cut-and-count analysis of the predicted and observed event yields separately in bins of ${{p_{\mathrm {T}}} (\gamma)}$ and for the three years of data taking using the input variations; the typical range across the three years is shown in the third column and can be compared between the different uncertainty sources. The last column gives the impact of each uncertainty on the measured inclusive ${\mathrm{t} \mathrm{\bar{t}}} \gamma$ cross section after the fit to the data, the so-called postfit uncertainties. |
png pdf |
Table 4:
Definition of the observables used in the differential cross section measurement. |
png pdf |
Table 5:
Summary of the one-dimensional CL intervals obtained for the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ from the interpretation of this result. The profiled results correspond to the fits where the other Wilson coefficient is left free in the fit, otherwise it is set to zero. |
png pdf |
Table 6:
Summary of the one-dimensional CL intervals obtained for the Wilson coefficients ${c_{\mathrm{t} \mathrm{Z}}}$ and ${c_{\mathrm{t} \mathrm{Z}}^{\mathrm {I}}}$ from the combined interpretation of this result and the lepton+jets result from Ref. [7]. The profiled results correspond to the fits where the other Wilson coefficient is left free in the fit, otherwise it is set to zero. |
| Summary |
|
A cross section measurement of top quark pair production in association with a photon (${\mathrm{t\bar{t}}\gamma} $), using 138 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}=$ 13 TeV recorded with the CMS detector at the CERN LHC, has been presented. The analysis is performed in a fiducial phase space defined by the requirement of exactly one isolated photon, exactly two oppositely charged leptons, and at least one b jet at particle level, including the ${\mathrm{e^{+}}\mathrm{e^{-}}} $, ${\mathrm{e^{\pm}}\mu^{\mp}} $, and $\mu^{+}\mu^{-}$ channels of the $\mathrm{t\bar{t}}$ decay. The inclusive cross section is extracted with a template fit to the transverse momentum distribution of the reconstructed photon, and is measured to be ${\sigma_\text{fid}} (\mathrm{ pp \to t\bar{t}\gamma })=$ 174.4 $\pm$ 2.5 (stat) $\pm$ 6.1(syst) fb, in good agreement with the standard model prediction of ${\sigma_\text{SM}} (\mathrm{ pp \to t\bar{t}\gamma })= $ 153 $\pm$ 25 fb. Differential cross sections are measured as functions of various kinematic properties of the photon, leptons, and jet, and unfolded to particle level. The comparison to standard model predictions is performed using different parton shower algorithms. The measurement is also interpreted in terms of the standard model effective field theory. Constraints are derived on the Wilson coefficients ${c_{\mathrm{t}\mathrm{Z}}}$ and ${c_{\mathrm{t}\mathrm{Z}}^{\mathrm{I}}}$ describing the modifications of the ${\mathrm{t\bar{t}}\mathrm{Z}}$ and ${\mathrm{t\bar{t}}\gamma} $ interaction vertices. From a combined interpretation of this measurement and another CMS measurement of ${\mathrm{t\bar{t}}\gamma} $ production using the single-lepton final state and the same data set, the best limits on these Wilson coefficients to date are derived. |
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