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| CMS-TOP-18-008 ; CERN-EP-2018-328 | ||
| Observation of single top quark production in association with a Z boson in proton-proton collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 14 December 2018 | ||
| Phys. Rev. Lett. 122 (2019) 132003 | ||
| Abstract: The observation of single top quark production in association with a Z boson and a quark ($\mathrm{t Z q} $ ) is reported. Events from proton-proton collisions at a center-of-mass energy of 13 TeV containing three charged leptons (either electrons or muons) and at least two jets are analyzed. The data were collected with the CMS detector in 2016 and 2017, and correspond to an integrated luminosity of 77.4 fb$^{-1}$. The increased integrated luminosity, a multivariate lepton identification, and a redesigned analysis strategy improve significantly the sensitivity of the analysis compared to previous searches for $\mathrm{t Z q} $ production. The $\mathrm{t Z q} $ signal is observed with a significance well over five standard deviations. The measured $\mathrm{t Z q} $ production cross section is $\sigma ({\mathrm{p}}{\mathrm{p}} \to \mathrm{t Z q} \to \mathrm{t} \ell^{+} \ell^{-} \mathrm{q} )= $ 111 $\pm$ 13 (stat) $ _{-9}^{+11}$ (syst) fb, for dilepton invariant masses above 30 GeV, in agreement with the standard model expectation. | ||
| Links: e-print arXiv:1812.05900 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures & Tables | Summary | Additional Figures & Tables | References | CMS Publications |
|---|
| Figures | |
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Figure 1:
Observed (points) and post-fit expected (shaded histograms) BDT distributions for events in SR-2/3j-1b (left), SR-4j-1b (middle), and SR-2b (right). The vertical bars on the points represent the statistical uncertainties in data. The hatched regions show the total uncertainties in the background. The lower panels display the ratio of the observed data to the predictions, including the ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure 1-a:
Observed (points) and post-fit expected (shaded histograms) BDT distributions for events in SR-2/3j-1b. The vertical bars on the points represent the statistical uncertainties in data. The hatched regions show the total uncertainties in the background. The lower panel displays the ratio of the observed data to the predictions, including the ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure 1-b:
Observed (points) and post-fit expected (shaded histograms) BDT distributions for events in SR-4j-1b. The vertical bars on the points represent the statistical uncertainties in data. The hatched regions show the total uncertainties in the background. The lower panel displays the ratio of the observed data to the predictions, including the ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure 1-c:
Observed (points) and post-fit expected (shaded histograms) BDT distributions for events in SR-2b. The vertical bars on the points represent the statistical uncertainties in data. The hatched regions show the total uncertainties in the background. The lower panel displays the ratio of the observed data to the predictions, including the ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure A1:
Observed (points) and post-fit expected distributions (shaded histograms) in SR-2/3j-1b events for the two most discriminating variables used in the BDT discriminant, the maximum dijet invariant mass among all pairs of jets in the event (left), and the ${{| \eta |}}$ of the recoiling jet (middle). The right plot shows the ${p_{\mathrm {T}}}$ of the Z boson, reconstructed from its leptonic decay products, for events with BDT discriminant values in excess of 0.5 in SR-2/3j-1b. This observable is highly sensitive to the presence of new physics phenomena. The vertical bars on the points give the statistical uncertainty in data, and the hatched regions display the total uncertainty in the prediction. The lower panels display the ratio of the observed data to the predictions, including the ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure A1-a:
Observed (points) and post-fit expected distributions (shaded histograms) in SR-2/3j-1b events for the maximum dijet invariant mass among all pairs of jets in the event.The vertical bars on the points give the statistical uncertainty in data, and the hatched regions display the total uncertainty in the prediction. The lower panel displays the ratio of the observed data to the predictions, including the ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure A1-b:
Observed (points) and post-fit expected distributions (shaded histograms) in SR-2/3j-1b events for the ${{| \eta |}}$ of the recoiling jet. The vertical bars on the points give the statistical uncertainty in data, and the hatched regions display the total uncertainty in the prediction. The lower panel displays the ratio of the observed data to the predictions, including the ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure A1-c:
The plot shows the ${p_{\mathrm {T}}}$ of the Z boson, reconstructed from its leptonic decay products, for events with BDT discriminant values in excess of 0.5 in SR-2/3j-1b. This observable is highly sensitive to the presence of new physics phenomena. The vertical bars on the points give the statistical uncertainty in data, and the hatched regions display the total uncertainty in the prediction. The lower panel displays the ratio of the observed data to the predictions, including the ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure A2:
Observed (points) and pre-fit expected distributions (shaded histograms) of the number of jets in the event for the WZ (left), and ZZ (right) control regions. The vertical bars on the points give the statistical uncertainty in data, and the hatched regions display the total uncertainty in the prediction. The lower panels display the ratio of the observed data to the predictions, including the tZq signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure A2-a:
Observed (points) and pre-fit expected distributions (shaded histograms) of the number of jets in the event for the WZ control region. The vertical bars on the points give the statistical uncertainty in data, and the hatched regions display the total uncertainty in the prediction. The lower panel displays the ratio of the observed data to the predictions, including the tZq signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
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Figure A2-b:
Observed (points) and pre-fit expected distributions (shaded histograms) of the number of jets in the event for the ZZ control region. The vertical bars on the points give the statistical uncertainty in data, and the hatched regions display the total uncertainty in the prediction. The lower panel displays the ratio of the observed data to the predictions, including the tZq signal, with inner and outer shaded bands, respectively, representing the statistical and total uncertainties in the predictions. |
| Tables | |
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Table A1:
Post-fit expected background and ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal event yields with their total uncertainties, and observed number of events in data in each of the signal regions. |
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Table A2:
Average impact on the measured tZq signal strength for major sources of systematic uncertainty. The impact of a particular nuisance parameter on the signal strength is computed by shifting the nuisance parameter by one standard deviation up and down from its post-fit value and recomputing the signal strength. All other nuisances are profiled as in the nominal fit when doing this computation. |
| Summary |
| In summary, we have reported the observation of single top quark production in association with a Z boson and a quark, $\mathrm{t Z q} $, using the leptonic $\mathrm{t Z q} $ decay mode. The $\mathrm{t Z q} $ signal is observed with a significance of well over five standard deviations. The $\mathrm{t Z q} $ production cross section is measured to be $\sigma(\mathrm{pp} \to \mathrm{t Z q} \to \mathrm{t} \ell^{+} \ell^{-} \mathrm{q}) =$ 111 $\pm$ 13 (stat) $ _{-9}^{+11}$ (syst) fb, where $\ell$ refers to an electron, muon, or $\tau$ lepton, for dilepton invariant masses in excess of 30 GeV, in agreement with the standard model prediction. |
| Additional Figures | |
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Additional Figure 1:
Efficiency of selecting prompt electrons (left), and muons (right) from simulated ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ and ${{\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {Z}}}$ events as a function of the misidentification probability for nonprompt leptons from simulated ${{\mathrm {t}\overline {\mathrm {t}}}}$ events for the lepton MVA (black and red lines for respectively 2016 and 2017 simulations), and for the cutoff-based lepton identification used in the previous CMS search for ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ (blue point). The black and red points correspond to the cut on the lepton MVA discriminator chosen for this analysis. |
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Additional Figure 1-a:
Efficiency of selecting prompt electrons from simulated ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ and ${{\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {Z}}}$ events as a function of the misidentification probability for nonprompt leptons from simulated ${{\mathrm {t}\overline {\mathrm {t}}}}$ events for the lepton MVA (black and red lines for respectively 2016 and 2017 simulations), and for the cutoff-based lepton identification used in the previous CMS search for ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ (blue point). The black and red points correspond to the cut on the lepton MVA discriminator chosen for this analysis. |
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Additional Figure 1-b:
Efficiency of selecting prompt muons from simulated ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ and ${{\mathrm {t}} {\overline {\mathrm {t}}} {\mathrm {Z}}}$ events as a function of the misidentification probability for nonprompt leptons from simulated ${{\mathrm {t}\overline {\mathrm {t}}}}$ events for the lepton MVA (black and red lines for respectively 2016 and 2017 simulations), and for the cutoff-based lepton identification used in the previous CMS search for ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ (blue point). The black and red points correspond to the cut on the lepton MVA discriminator chosen for this analysis. |
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Additional Figure 2:
Expected and observed distributions in the ${{\mathrm {W}} {\mathrm {Z}}}$ control region of the $| \eta |$ of the recoiling jet (left), the maximum dijet invariant mass out of any combination of jets in the event (middle), and the asymmetry of the lepton not forming the Z boson candidate ($\ell _{W}$), defined as its $| \eta |$ multiplied by its charge (right). |
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Additional Figure 2-a:
Expected and observed distributions in the ${{\mathrm {W}} {\mathrm {Z}}}$ control region of the $| \eta |$ of the recoiling jet. the maximum dijet invariant mass out of any combination of jets in the event. |
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Additional Figure 2-b:
Expected and observed distributions in the ${{\mathrm {W}} {\mathrm {Z}}}$ control region of the maximum dijet invariant mass out of any combination of jets in the event. |
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Additional Figure 2-c:
Expected and observed distributions in the ${{\mathrm {W}} {\mathrm {Z}}}$ control region of the asymmetry of the lepton not forming the Z boson candidate ($\ell _{W}$), defined as its $| \eta |$ multiplied by its charge. |
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Additional Figure 3:
Expected and observed distributions in the ${{\mathrm {W}} {\mathrm {Z}}}$ control region of the highest lepton ${p_{\mathrm {T}}}$ (left), second highest lepton ${p_{\mathrm {T}}}$ (middle) and lowest lepton ${p_{\mathrm {T}}}$ (right). |
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Additional Figure 3-a:
Expected and observed distributions in the ${{\mathrm {W}} {\mathrm {Z}}}$ control region of the highest lepton ${p_{\mathrm {T}}}$. |
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Additional Figure 3-b:
Expected and observed distributions in the ${{\mathrm {W}} {\mathrm {Z}}}$ control region of the second highest lepton ${p_{\mathrm {T}}}$. |
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Additional Figure 3-c:
Expected and observed distributions in the ${{\mathrm {W}} {\mathrm {Z}}}$ control region of the lowest lepton ${p_{\mathrm {T}}}$. |
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Additional Figure 4:
Expected and observed distributions in the ${{\mathrm {Z}} {\mathrm {Z}}}$ control region of the highest $| \eta |$ value out of any jet in the event (left) and the maximum dijet invariant mass out of any combination of jets in the event (right). |
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Additional Figure 4-a:
Expected and observed distributions in the ${{\mathrm {Z}} {\mathrm {Z}}}$ control region of the highest $| \eta |$ value out of any jet in the event. Additional Figure 4-b |
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Additional Figure 4-b:
Expected and observed distributions in the ${{\mathrm {Z}} {\mathrm {Z}}}$ control region of the highest $| \eta |$ value out of any jet in the event (left) and the maximum dijet invariant mass out of any combination of jets in the event (right). |
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Additional Figure 5:
Comparison between the yields from simulated ${{\mathrm {t}\overline {\mathrm {t}}}}$ events where each lepton passes the full signal region lepton selection to the prediction of these yields obtained by taking events in which at least one lepton fails to pass the full selection to which the fake-rate, determined using QCD simulations, is applied, as a function of the minimum $\Delta R$ between any lepton and b jet in the event (left), and the lepton flavor composition of the event (right). |
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Additional Figure 5-a:
Comparison between the yields from simulated ${{\mathrm {t}\overline {\mathrm {t}}}}$ events where each lepton passes the full signal region lepton selection to the prediction of these yields obtained by taking events in which at least one lepton fails to pass the full selection to which the fake-rate, determined using QCD simulations, is applied, as a function of the minimum $\Delta R$ between any lepton and b jet in the event. |
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Additional Figure 5-b:
Comparison between the yields from simulated ${{\mathrm {t}\overline {\mathrm {t}}}}$ events where each lepton passes the full signal region lepton selection to the prediction of these yields obtained by taking events in which at least one lepton fails to pass the full selection to which the fake-rate, determined using QCD simulations, is applied, as a function of the lepton flavor composition of the event. |
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Additional Figure 6:
Comparison between the yields from simulated ${{\mathrm {t}\overline {\mathrm {t}}}}$ events where each lepton passes the full signal region lepton selection to the prediction of these yields obtained by taking events in which at least one lepton fails to pass the full selection to which the fake-rate, determined using QCD simulations, is applied, as a function of the minimum angular separation in terms of the maximum dijet invariant mass out of any combination of jets in the event (left), and the $| \eta |$ of the recoiling jet (right). |
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Additional Figure 6-a:
Comparison between the yields from simulated ${{\mathrm {t}\overline {\mathrm {t}}}}$ events where each lepton passes the full signal region lepton selection to the prediction of these yields obtained by taking events in which at least one lepton fails to pass the full selection to which the fake-rate, determined using QCD simulations, is applied, as a function of the minimum angular separation in terms of the maximum dijet invariant mass out of any combination of jets in the event. |
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Additional Figure 6-b:
Comparison between the yields from simulated ${{\mathrm {t}\overline {\mathrm {t}}}}$ events where each lepton passes the full signal region lepton selection to the prediction of these yields obtained by taking events in which at least one lepton fails to pass the full selection to which the fake-rate, determined using QCD simulations, is applied, as a function of the $| \eta |$ of the recoiling jet. |
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Additional Figure 7:
Observed and expected distributions of the $| \eta |$ of the recoiling jet (left), the maximum dijet invariant mass out of any combination of jets in the event (middle), and the lepton flavor composition of the event (right). The selected events are trilepton events that either have no pair of opposite sign and same flavor leptons, or events in which there is no dilepton pair with a mass close to that of the Z boson and where the trilepton invariant mass is not compatible with that of the Z boson. The events are required to have 2 or 3 jets, exactly one of which is b-tagged to further enrich the sample in nonprompt leptons. |
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Additional Figure 7-a:
Observed and expected distributions of the $| \eta |$ of the recoiling jet. The selected events are trilepton events that either have no pair of opposite sign and same flavor leptons, or events in which there is no dilepton pair with a mass close to that of the Z boson and where the trilepton invariant mass is not compatible with that of the Z boson. The events are required to have 2 or 3 jets, exactly one of which is b-tagged to further enrich the sample in nonprompt leptons. |
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Additional Figure 7-b:
Observed and expected distributions of the maximum dijet invariant mass out of any combination of jets in the event. The selected events are trilepton events that either have no pair of opposite sign and same flavor leptons, or events in which there is no dilepton pair with a mass close to that of the Z boson and where the trilepton invariant mass is not compatible with that of the Z boson. The events are required to have 2 or 3 jets, exactly one of which is b-tagged to further enrich the sample in nonprompt leptons. |
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Additional Figure 7-c:
Observed and expected distributions of the lepton flavor composition of the event. The selected events are trilepton events that either have no pair of opposite sign and same flavor leptons, or events in which there is no dilepton pair with a mass close to that of the Z boson and where the trilepton invariant mass is not compatible with that of the Z boson. The events are required to have 2 or 3 jets, exactly one of which is b-tagged to further enrich the sample in nonprompt leptons. |
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Additional Figure 8:
Observed and expected distributions of the BDT used for signal extraction in SR-2/3j-1b. The selected events are trilepton events that either have no pair of opposite sign and same flavor leptons, or events in which there is no dilepton pair with a mass close to that of the Z boson and where the trilepton invariant mass is not compatible with that of the Z boson. The events are required to have 2 or 3 jets, exactly one of which is b-tagged to further enrich the sample in nonprompt leptons. |
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Additional Figure 9:
Post-fit expected and observed distribution in SR-2/3j-1b of the asymmetry of the lepton not forming the Z boson candidate ($\ell _{W}$), defined as its $| \eta |$ multiplied by its charge. |
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Additional Figure 10:
Post-fit expected and observed distributions in the SR-2/3j-1b of the highest lepton ${p_{\mathrm {T}}}$ (left), second highest lepton ${p_{\mathrm {T}}}$ (middle) and lowest lepton ${p_{\mathrm {T}}}$ (right). |
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Additional Figure 10-a:
Post-fit expected and observed distributions in the SR-2/3j-1b of the highest lepton ${p_{\mathrm {T}}}$. |
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Additional Figure 10-b:
Post-fit expected and observed distributions in the SR-2/3j-1b of the second highest lepton ${p_{\mathrm {T}}}$. |
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Additional Figure 10-c:
Post-fit expected and observed distributions in the SR-2/3j-1b of the lowest lepton ${p_{\mathrm {T}}}$. |
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Additional Figure 11:
Post-fit expected and observed distributions in SR-4j-1b of the $| \eta |$ of the recoiling jet (left), the maximum dijet mass out of any combination of jets in the event (middle), and the number of jets in the event (right). |
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Additional Figure 11-a:
Post-fit expected and observed distributions in SR-4j-1b of the $| \eta |$ of the recoiling jet. |
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Additional Figure 11-b:
Post-fit expected and observed distributions in SR-4j-1b of the maximum dijet mass out of any combination of jets in the event. |
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Additional Figure 11-c:
Post-fit expected and observed distributions in SR-4j-1b of the number of jets in the event. |
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Additional Figure 12:
Post-fit expected and observed distributions in SR-4j-1b of the highest $| \eta |$ value out of any jet in the event. |
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Additional Figure 13:
Post-fit expected and observed distributions in SR-2b of the $| \eta |$ of the recoiling jet (left), the maximum dijet mass out of any combination of jets in the event (middle), and the number of jets in the event (right). |
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Additional Figure 13-a:
Post-fit expected and observed distributions in SR-2b of the $| \eta |$ of the recoiling jet. |
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Additional Figure 13-b:
Post-fit expected and observed distributions in SR-2b of the $| \eta |$ of the maximum dijet mass out of any combination of jets in the event. |
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Additional Figure 13-c:
Post-fit expected and observed distributions in SR-2b of the $| \eta |$ of the number of jets in the event. |
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Additional Figure 14:
Post-fit expected and observed distributions in SR-2b of the highest $| \eta |$ value out of any jet in the event. |
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Additional Figure 15:
Post-fit expected and observed distributions in SR-2/3j-1b events with BDT values greater than 0.5 of the $| \eta |$ of the recoiling jet (left), and the lepton flavor composition of the event (right). |
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Additional Figure 15-a:
Post-fit expected and observed distributions in SR-2/3j-1b events with BDT values greater than 0.5 of the $| \eta |$ of the recoiling jet. |
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Additional Figure 15-b:
Post-fit expected and observed distributions in SR-2/3j-1b events with BDT values greater than 0.5 of the lepton flavor composition of the event. |
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Additional Figure 16:
Post-fit expected and observed distributions in SR-2/3j-1b events with BDT values greater than 0.5 of the highest lepton ${p_{\mathrm {T}}}$ (left), second highest lepton ${p_{\mathrm {T}}}$ (middle) and lowest lepton ${p_{\mathrm {T}}}$ (right). |
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Additional Figure 16-a:
Post-fit expected and observed distributions in SR-2/3j-1b events with BDT values greater than 0.5 of the highest lepton ${p_{\mathrm {T}}}$. |
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Additional Figure 16-b:
Post-fit expected and observed distributions in SR-2/3j-1b events with BDT values greater than 0.5 of the second highest lepton ${p_{\mathrm {T}}}$. |
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Additional Figure 16-c:
Post-fit expected and observed distributions in SR-2/3j-1b events with BDT values greater than 0.5 of the lowest lepton ${p_{\mathrm {T}}}$. |
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Additional Figure 17:
Post-fit expected and observed distributions in SR-4j-1b events with BDT values greater than 0.5 of the $| \eta |$ of the recoiling jet (left), the ${p_{\mathrm {T}}}$ of the Z boson reconstructed from the dilepton pair of invariant mass closest to the mass of the Z boson (middle), and the lepton flavor composition of the event (right). |
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Additional Figure 17-a:
Post-fit expected and observed distributions in SR-4j-1b events with BDT values greater than 0.5 of the $| \eta |$ of the recoiling jet. |
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Additional Figure 17-b:
Post-fit expected and observed distributions in SR-4j-1b events with BDT values greater than 0.5 of the ${p_{\mathrm {T}}}$ of the Z boson reconstructed from the dilepton pair of invariant mass closest to the mass of the Z boson. |
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Additional Figure 17-c:
Post-fit expected and observed distributions in SR-4j-1b events with BDT values greater than 0.5 of the lepton flavor composition of the event. |
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Additional Figure 18:
Post-fit expected and observed distributions in SR-2b events with BDT values greater than 0.5 of the $| \eta |$ of the recoiling jet (left), the ${p_{\mathrm {T}}}$ of the Z boson reconstructed from the dilepton pair of invariant mass closest to the mass of the Z boson (middle), and the lepton flavor composition of the event (right). |
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Additional Figure 18-a:
Post-fit expected and observed distributions in SR-2b events with BDT values greater than 0.5 of the $| \eta |$ of the recoiling jet. |
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Additional Figure 18-b:
Post-fit expected and observed distributions in SR-2b events with BDT values greater than 0.5 of the ${p_{\mathrm {T}}}$ of the Z boson reconstructed from the dilepton pair of invariant mass closest to the mass of the Z boson. |
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Additional Figure 18-c:
Post-fit expected and observed distributions in SR-2b events with BDT values greater than 0.5 of the lepton flavor composition of the event. |
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Additional Figure 19:
Event display of a 2016 data event in SR-2/3j-1b with a very high BDT score, which is thus highly likely to come from ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ production. In the event, two electrons forming a Z mass, a muon, a b jet and a forward jet can be seen, as would be expected in a ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ event. Electrons (muons) are highlighted in green (red), while jets are represented as orange cones. |
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Additional Figure 20:
Event display of a 2016 data event in SR-2/3j-1b with a very high BDT score, which is thus highly likely to come from ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ production. In the event, two electrons forming a Z mass, a muon, a b jet and a forward jet can be seen, as would be expected in a ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ event. Electrons (muons) are highlighted in green (red), while jets are represented as orange cones. |
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Additional Figure 21:
Event display of a 2016 data event in SR-2/3j-1b with a very high BDT score, which is thus highly likely to come from ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ production. In the event, two electrons forming a Z mass, a muon, a b jet and a forward jet can be seen, as would be expected in a ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ event. Electrons (muons) are highlighted in green (red), while jets are represented as orange cones. |
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Additional Figure 22:
Event display of a 2016 data event in SR-2/3j-1b with a very high BDT score, which is thus highly likely to come from ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ production. In the event, two electrons forming a Z mass, a muon, a b jet and a forward jet can be seen, as would be expected in a ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ event. Electrons (muons) are highlighted in green (red), while jets are represented as orange cones. |
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Additional Figure 23:
Event display of a 2017 data event in SR-2/3j-1b with a very high BDT score, which is thus highly likely to come from ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ production. In the event, two muons forming a Z mass, an electron, a b jet and a forward jet can be seen, as would be expected in a ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ event. Electrons (muons) are highlighted in green (red), while jets are represented as orange cones.21 |
| Additional Tables | |
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Additional Table 1:
Average impact on the measured ${\mathrm {t}} {\mathrm {Z}} {\mathrm {q}}$ signal strength for major sources of systematic uncertainty. The impact of a particular nuisance parameter on the signal strength is computed by shifting the nuisance parameter by one standard deviation up and down from its post-fit value and recomputing the signal strength. All other nuisances are profiled as in the nominal fit when doing this computation. |
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