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| CMS-TOP-19-009 ; CERN-EP-2021-124 | ||
| Measurement of the top quark mass using events with a single reconstructed top quark in pp collisions at $\sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 24 August 2021 | ||
| JHEP 12 (2021) 161 | ||
| Abstract: A measurement of the top quark mass is performed using a data sample enriched with single top quark events produced in the $t$ channel. The study is based on proton-proton collision data, corresponding to an integrated luminosity of 35.9 fb$^{-1}$, recorded at $\sqrt{s} = $ 13 TeV by the CMS experiment at the LHC in 2016. Candidate events are selected by requiring an isolated high-momentum lepton (muon or electron) and exactly two jets, of which one is identified as originating from a bottom quark. Multivariate discriminants are designed to separate the signal from the background. Optimized thresholds are placed on the discriminant outputs to obtain an event sample with high signal purity. The top quark mass is found to be 172.13$^{+0.76}_{-0.77}$ GeV, where the uncertainty includes both the statistical and systematic components, reaching sub-GeV precision for the first time in this event topology. The masses of the top quark and antiquark are also determined separately using the lepton charge in the final state, from which the mass ratio and difference are determined to be 0.9952$^{+0.0079}_{-0.0104}$ and 0.83$^{+1.79}_{-1.35}$ GeV, respectively. The results are consistent with CPT invariance. | ||
| Links: e-print arXiv:2108.10407 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
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Figure 1:
Feynman diagrams of the $t$-channel single top quark production at LO corresponding to four- (left) and five-flavor (right) schemes. At NLO in perturbative QCD, the left diagram is also part of the five-flavor scheme. |
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Figure 1-a:
Feynman diagram of the $t$-channel single top quark production at LO corresponding to four-flavor scheme. At NLO in perturbative QCD, the diagram is also part of the five-flavor scheme. |
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Figure 1-b:
Feynman diagram of the $t$-channel single top quark production at LO corresponding to five-flavor scheme. |
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Figure 2:
Event yields corresponding to positively and negatively charged muons (left) and electrons (right) in the final states obtained for the 2J1T category from data (points) and from simulated signal and background processes (colored histograms). The vertical bars on the points show the statistical uncertainty in the data, and the cross-hatched bands denote the quadrature sum of the statistical and systematic uncertainties in the predictions. The lower panels show the ratio of the data to the predictions. |
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Figure 2-a:
Event yields corresponding to positively and negatively charged muons in the final states obtained for the 2J1T category from data (points) and from simulated signal and background processes (colored histograms). The vertical bars on the points show the statistical uncertainty in the data, and the cross-hatched bands denote the quadrature sum of the statistical and systematic uncertainties in the predictions. The lower panel shows the ratio of the data to the predictions. |
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Figure 2-b:
Event yields corresponding to positively and negatively charged electrons in the final states obtained for the 2J1T category from data (points) and from simulated signal and background processes (colored histograms). The vertical bars on the points show the statistical uncertainty in the data, and the cross-hatched bands denote the quadrature sum of the statistical and systematic uncertainties in the predictions. The lower panel shows the ratio of the data to the predictions. |
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Figure 3:
Postfit distributions of ${m_{\mathrm {T}}}$ for the muon (left) and electron (right) final states in the 2J0T (upper) and 2J1T (lower) categories for the data (points) and the various components of the fit (colored lines). The lower panels show the ratio of the data to the fit predictions. The bands represent the postfit uncertainty in the ${m_{\mathrm {T}}}$ distribution predicted by the fit. |
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Figure 3-a:
Postfit distribution of ${m_{\mathrm {T}}}$ for the muon final state in the 2J0T category for the data (points) and the various components of the fit (colored lines). The lower panel shows the ratio of the data to the fit predictions. The bands represent the postfit uncertainty in the ${m_{\mathrm {T}}}$ distribution predicted by the fit. |
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Figure 3-b:
Postfit distribution of ${m_{\mathrm {T}}}$ for the electron final state in the 2J0T category for the data (points) and the various components of the fit (colored lines). The lower panel shows the ratio of the data to the fit predictions. The bands represent the postfit uncertainty in the ${m_{\mathrm {T}}}$ distribution predicted by the fit. |
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Figure 3-c:
Postfit distribution of ${m_{\mathrm {T}}}$ for the muon final state in the 2J1T category for the data (points) and the various components of the fit (colored lines). The lower panel shows the ratio of the data to the fit predictions. The bands represent the postfit uncertainty in the ${m_{\mathrm {T}}}$ distribution predicted by the fit. |
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Figure 3-d:
Postfit distribution of ${m_{\mathrm {T}}}$ for the electron final state in the 2J1T category for the data (points) and the various components of the fit (colored lines). The lower panel shows the ratio of the data to the fit predictions. The bands represent the postfit uncertainty in the ${m_{\mathrm {T}}}$ distribution predicted by the fit. |
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Figure 4:
Data and simulation comparison for $\Delta R_{\mathrm{b} \mathrm {j^{\prime}}}$ (upper row), untagged jet $ {| \eta |}$ (middle row), and BDT response (lower row) in the 2J1T category for the muon (left) and electron (right) final states. The lower panels show the ratio of the data to simulation predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin in each of the upper-row plots includes the overflow. |
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Figure 4-a:
Data and simulation comparison for $\Delta R_{\mathrm{b} \mathrm {j^{\prime}}}$ in the 2J1T category for the muon final state. The lower panel shows the ratio of the data to simulation predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. |
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Figure 4-b:
Data and simulation comparison for $\Delta R_{\mathrm{b} \mathrm {j^{\prime}}}$ in the 2J1T category for the electron final state. The lower panel shows the ratio of the data to simulation predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. |
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Figure 4-c:
Data and simulation comparison for the untagged jet $ {| \eta |}$ in the 2J1T category for the muon final state. The lower panel shows the ratio of the data to simulation predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. |
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Figure 4-d:
Data and simulation comparison for the untagged jet $ {| \eta |}$ in the 2J1T category for the electron final state. The lower panel shows the ratio of the data to simulation predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. |
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Figure 4-e:
Data and simulation comparison for the BDT response in the 2J1T category for the muon final state. The lower panel shows the ratio of the data to simulation predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. |
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Figure 4-f:
Data and simulation comparison for the BDT response in the 2J1T category for the electron final state. The lower panel shows the ratio of the data to simulation predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. |
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Figure 5:
Combined BDT performance in terms of the ROC curve (upper left), and the signal and background efficiencies and signal purity as functions of the BDT selection threshold (upper right) in the muon and electron final states. The uncertainty in ${m_{\mathrm{t}}}$ from the combined statistical and profiled systematic components (red curve), and from the mass calibration (blue curve) as a function of the BDT selection threshold (lower left). Arrows on the plots indicate the region of better separation (upper left) and optimized selection criteria (upper right and lower left). A comparison of the reconstructed ${m_{\mathrm{t}}}$ shapes from simulated signal events for different selection thresholds on the BDT response is shown on the lower right. The lower panel shows the ratio relative to the case where no selection (red) is applied, with the grey band denoting the prefit rate uncertainty around the red curve. |
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Figure 5-a:
Combined BDT performance in terms of the ROC curve in the muon and electron final states. The arrow indicates the region of better separation. |
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Figure 5-b:
The signal and background efficiencies and signal purity as functions of the BDT selection threshold in the muon and electron final states. The arrow indicates the region of optimized selection criteria. |
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Figure 5-c:
The uncertainty in ${m_{\mathrm{t}}}$ from the combined statistical and profiled systematic components (red curve), and from the mass calibration (blue curve) as a function of the BDT selection threshold. The arrow indicates the region of optimized selection criteria. |
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Figure 5-d:
A comparison of the reconstructed ${m_{\mathrm{t}}}$ shapes from simulated signal events for different selection thresholds on the BDT response. The lower panel shows the ratio relative to the case where no selection (red) is applied, with the grey band denoting the prefit rate uncertainty around the red curve. |
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Figure 6:
Reconstructed ${m_{\mathrm{t}}}$ distributions before (upper-left) and after (upper-right) applying the optimized BDT selection from data (points) and simulation (colored histograms) are shown in the upper row. The lower-left plot shows the event yields per lepton charge in data and simulation after optimized BDT selection. Data-to-simulation comparison of the fit variable $\zeta \ = \ \ln({m_{\mathrm{t}}} /\text{1 GeV})$ inclusive of lepton charge after optimized BDT selection is presented in the lower right plot. The horizontal bars in the upper-right plot indicate the variable bin width. The first and last bins include the underflow and overflow, respectively, for each plot. The bands denote a quadrature sum of the statistical and systematic uncertainties in the prediction. The lower panels show the ratio of the data to the prediction. The deviation from unity seen in the first bins of the upper-right and lower-right ratio plots arises because of significantly less underflow events in the data compared to the simulation. |
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Figure 6-a:
Reconstructed ${m_{\mathrm{t}}}$ distributions before applying the optimized BDT selection from data (points) and simulation (colored histograms). The first and last bins include the underflow and overflow, respectively. The bands denote a quadrature sum of the statistical and systematic uncertainties in the prediction. The lower panel shows the ratio of the data to the prediction. |
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Figure 6-b:
Reconstructed ${m_{\mathrm{t}}}$ distributions after applying the optimized BDT selection from data (points) and simulation (colored histograms). The horizontal bars indicate the variable bin width. The first and last bins include the underflow and overflow, respectively. The bands denote a quadrature sum of the statistical and systematic uncertainties in the prediction. The lower panel shows the ratio of the data to the prediction. The deviation from unity seen in the first bin arises because of significantly less underflow events in the data compared to the simulation. |
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Figure 6-c:
The plot shows the event yields per lepton charge in data and simulation after optimized BDT selection. The bands denote a quadrature sum of the statistical and systematic uncertainties in the prediction. The lower panel shows the ratio of the data to the prediction. |
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Figure 6-d:
Data-to-simulation comparison of the fit variable $\zeta \ =\ \ln({m_{\mathrm{t}}} /\text{1 GeV})$ inclusive of lepton charge after optimized BDT selection. The first and last bins include the underflow and overflow, respectively. The bands denote a quadrature sum of the statistical and systematic uncertainties in the prediction. The lower panel shows the ratio of the data to the prediction. The deviation from unity seen in the first bin arises because of significantly less underflow events in the data compared to the simulation. |
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Figure 7:
Postfit distributions of $\zeta \ =\ \ln({m_{\mathrm{t}}} /\text{1 GeV})$ for the $\ell^{+}$ (upper left), $\ell^{-}$ (upper right), and $\ell^{\pm}$ (lower row) final states for signal and background processes compared to data in the 2J1T category. The lower panels show the pulls. The postfit signal and background shapes for each lepton flavor are combined in these plots for a comparison with data for the three different cases based on the lepton charge. |
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Figure 7-a:
Postfit distribution of $\zeta \ =\ \ln({m_{\mathrm{t}}} /\text{1 GeV})$ for the $\ell^{+}$ final state for signal and background processes compared to data in the 2J1T category. The lower panel shows the pulls. The postfit signal and background shapes for each lepton flavor are combined for a comparison with data for the three different cases based on the lepton charge. |
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Figure 7-b:
Postfit distribution of $\zeta \ =\ \ln({m_{\mathrm{t}}} /\text{1 GeV})$ for the $\ell^{-}$ final state for signal and background processes compared to data in the 2J1T category. The lower panel shows the pulls. The postfit signal and background shapes for each lepton flavor are combined for a comparison with data for the three different cases based on the lepton charge. |
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Figure 7-c:
Postfit distribution of $\zeta \ =\ \ln({m_{\mathrm{t}}} /\text{1 GeV})$ for the $\ell^{\pm}$ final state for signal and background processes compared to data in the 2J1T category. The lower panel shows the pulls. The postfit signal and background shapes for each lepton flavor are combined for a comparison with data for the three different cases based on the lepton charge. |
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Figure 8:
Test of the linearity of the postfit top quark mass $m_{\text {fit}}$ for different values of true mass $m_{\text {true}}$ (left), and the resulting mass calibration $\Delta m_{\mathrm {cal}}$ as a function of $m_{\text {fit}}$ (right) for events in the 2J1T category for the $\ell^{+}$ (upper), $\ell^{-}$ (middle), and $\ell^{\pm}$ (lower) cases. The shaded regions indicate $\pm $1 standard deviations about the central values defined by the red line. The value of the $\chi ^{2}$ per degrees of freedom (dof) from the linear fit is shown in each plot. |
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Figure 8-a:
Test of the linearity of the postfit top quark mass $m_{\text {fit}}$ for different values of true mass $m_{\text {true}}$ for events in the 2J1T category for the $\ell^{+}$ case. The shaded region indicates $\pm $1 standard deviations about the central values defined by the red line. The value of the $\chi ^{2}$ per degrees of freedom (dof) from the linear fit is shown. |
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Figure 8-b:
Mass calibration $\Delta m_{\mathrm {cal}}$ as a function of $m_{\text {fit}}$ for events in the 2J1T category for the |
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Figure 8-c:
Test of the linearity of the postfit top quark mass $m_{\text {fit}}$ for different values of true mass $m_{\text {true}}$ for events in the 2J1T category for the $\ell^{-}$ case. The shaded region indicates $\pm $1 standard deviations about the central values defined by the red line. The value of the $\chi ^{2}$ per degrees of freedom (dof) from the linear fit is shown. |
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Figure 8-d:
Mass calibration $\Delta m_{\mathrm {cal}}$ as a function of $m_{\text {fit}}$ for events in the 2J1T category for the |
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Figure 8-e:
Test of the linearity of the postfit top quark mass $m_{\text {fit}}$ for different values of true mass $m_{\text {true}}$ for events in the 2J1T category for the $\ell^{\pm}$ case. The shaded region indicates $\pm $1 standard deviations about the central values defined by the red line. The value of the $\chi ^{2}$ per degrees of freedom (dof) from the linear fit is shown. |
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Figure 8-f:
Mass calibration $\Delta m_{\mathrm {cal}}$ as a function of $m_{\text {fit}}$ for events in the 2J1T category for the |
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Figure 9:
A comparison of measured ${m_{\mathrm{t}}}$ values from this analysis (black circle), from previous CMS results in ${\mathrm{t} {}\mathrm{\bar{t}}}$ events at $\sqrt {s} = $ 13 TeV for fully hadronic [10], dileptonic [14], and semileptonic [9] final states, and from ATLAS [7] and CMS [8,22] analyses at $\sqrt {s} = $ 8 TeV. The horizontal bars on the points show the combined statistical and systematic uncertainties in each measurement. The vertical dashed black line indicates the central value obtained from this measurement in the $\ell^{\pm}$ final state. The green band represents the combined statistical and profiled systematic uncertainties in the present result, whereas the yellow band shows the total uncertainty. |
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Figure 10:
A comparison of the $\Delta {m_{\mathrm{t}}} $ measurement from this analysis (black circle) with the previous ATLAS [90] and CMS [91] results in ${\mathrm{t} {}\mathrm{\bar{t}}}$ events at 7 and 8 TeV, respectively. The horizontal bars on the points show the combined statistical and systematic uncertainties in each measurement. The vertical dashed black line indicates the central value obtained from this measurement, and the vertical dash-dotted magenta line is the SM prediction. The green band represents the combined statistical and profiled systematic uncertainties in the present result, whereas the yellow band shows the total uncertainty. |
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Figure A1:
Distributions of $m_{\mathrm{b} \mathrm {j^{\prime}}}$ (upper row), $\cos{\theta ^{*}}$ (middle row), and ${m_{\mathrm {T}}}$ (lower row) for the muon (left) and electron (right) final states in the 2J1T category for data (points) and simulation (colored histograms). The lower panel in each plot shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin in each of the upper- and lower-row plots includes the overflow. |
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Figure A1-a:
Distribution of $m_{\mathrm{b} \mathrm {j^{\prime}}}$ the muon final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin includes the overflow. |
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Figure A1-b:
Distribution of $m_{\mathrm{b} \mathrm {j^{\prime}}}$ the electron final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin includes the overflow. |
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Figure A1-c:
Distribution of $\cos{\theta ^{*}}$ the muon final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. |
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Figure A1-d:
Distribution of $\cos{\theta ^{*}}$ the electron final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. |
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Figure A1-e:
Distribution of ${m_{\mathrm {T}}}$ the muon final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin includes the overflow. |
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Figure A1-f:
Distribution of ${m_{\mathrm {T}}}$ the electron final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin includes the overflow. |
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Figure A2:
Distributions of $ {| \Delta \eta _{l\mathrm{b}} |}$ (upper row) and $ {p_{\mathrm {T}}} ^{\mathrm{b}} + {p_{\mathrm {T}}} ^{\mathrm {j}^{\prime}}$ (middle row) for the muon (left) and electron (right) final states in the 2J1T category for data (points) and simulation (colored histograms). The lower row shows the similar data-to-simulation comparison for $ {| \eta _{\ell} |}$ (left) and FW1 (right) for the muon (left) and electron (right) final states in the 2J1T category. The lower panel in each plot shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin in each plot except for the lower-right one includes the overflow. |
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Figure A2-a:
Distribution of $ {| \Delta \eta _{l\mathrm{b}} |}$ $ {p_{\mathrm {T}}} ^{\mathrm{b}} + {p_{\mathrm {T}}} ^{\mathrm {j}^{\prime}}$ for the muon final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin includes the overflow. |
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Figure A2-b:
Distribution of $ {| \Delta \eta _{l\mathrm{b}} |}$ $ {p_{\mathrm {T}}} ^{\mathrm{b}} + {p_{\mathrm {T}}} ^{\mathrm {j}^{\prime}}$ for the electron final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin includes the overflow. |
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Figure A2-c:
Distribution of $ {| \Delta \eta _{l\mathrm{b}} |}$ $ {p_{\mathrm {T}}} ^{\mathrm{b}} + {p_{\mathrm {T}}} ^{\mathrm {j}^{\prime}}$ for the muon final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin includes the overflow. |
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Figure A2-d:
Distribution of $ {| \Delta \eta _{l\mathrm{b}} |}$ $ {p_{\mathrm {T}}} ^{\mathrm{b}} + {p_{\mathrm {T}}} ^{\mathrm {j}^{\prime}}$ for the electron final state in the 2J1T category for data (points) and simulation (colored histograms). The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin includes the overflow. |
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Figure A2-e:
Distribution of $ {| \eta _{\ell} |}$ for the muon final state in the 2J1T category. The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. The last bin includes the overflow. |
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Figure A2-f:
Distribution of FW1 for the electron final state in the 2J1T category. The lower panel shows the ratio of the data to the predictions. The bands indicate the prefit statistical and systematic uncertainties added in quadrature. |
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Figure A3:
Correlations in % among the BDT input variables used for the muon (left) and electron (right) final states in the signal and background events of the 2J1T category before (upper-two rows) and after (lower-two rows) decorrelation. |
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Figure A3-a:
Correlations in % among two BDT input variables used for the muon final state in the signal and background events of the 2J1T category before decorrelation. |
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Figure A3-b:
Correlations in % among two BDT input variables used for the electron final state in the signal and background events of the 2J1T category before decorrelation. |
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Figure A3-c:
Correlations in % among two BDT input variables used for the muon final state in the signal and background events of the 2J1T category before decorrelation. |
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Figure A3-d:
Correlations in % among two BDT input variables used for the electron final state in the signal and background events of the 2J1T category before decorrelation. |
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Figure A3-e:
Correlations in % among two BDT input variables used for the muon final state in the signal and background events of the 2J1T category after decorrelation. |
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Figure A3-f:
Correlations in % among two BDT input variables used for the electron final state in the signal and background events of the 2J1T category after decorrelation. |
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Figure A3-g:
Correlations in % among two BDT input variables used for the muon final state in the signal and background events of the 2J1T category after decorrelation. |
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Figure A3-h:
Correlations in % among two BDT input variables used for the electron final state in the signal and background events of the 2J1T category after decorrelation. |
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Figure B1:
Scan of the profile likelihood ratio as a function of the POI for the parametric fit model used in the $\ell^{\pm}$ final state of the 2J1T category in data and simulated events (left). Correlations in % among the POI and nuisance parameters corresponding to the fit to data for the $\ell^{\pm}$ final state of the 2J1T category (right). |
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Figure B1-a:
Scan of the profile likelihood ratio as a function of the POI for the parametric fit model used in the $\ell^{\pm}$ final state of the 2J1T category in data and simulated events. |
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Figure B1-b:
Correlations in % among the POI and nuisance parameters corresponding to the fit to data for the $\ell^{\pm}$ final state of the 2J1T category. |
| Tables | |
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Table 1:
BDT input variables ranked in decreasing order of their \textit {SP} values for the muon and electron final states in the 2J1T category. |
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Table 2:
Summary of the ${m_{\mathrm{t}}}$ systematic uncertainties in GeV for each final-state lepton charge configuration, as discussed in Section 8. With the exception of the flavor-dependent JES sources, the total systematic uncertainty is obtained from the quadrature sum of the individual systematic sources. The statistical uncertainties in the systematic shifts are quoted within parentheses whenever alternative simulated samples with systematic variations have been used. These statistical uncertainties are determined from 1000 pseudo-experiments in each case. |
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Table 3:
Summary of the ${m_{\mathrm{t}}}$ uncertainties in GeV for each final-state lepton charge configuration. The statistical uncertainties are obtained by performing the fits again in each case while fixing the nuisance parameters to their estimated values from data. With the exception of the flavor-dependent JES sources, the total systematic uncertainty is obtained from the quadrature sum of the individual systematic sources. The amount of statistical fluctuations in the systematic shifts are quoted within parentheses whenever alternative simulated samples with systematic variations have been used. These are determined from 1000 pseudo-experiments in each case. Entries with $<$ 0.01 denote that the magnitude of the systematic bias is less than 0.01. |
| Summary |
| Measurements of the top quark and antiquark masses, as well as their ratio and difference, are performed using a data sample enriched with single top quark events produced in proton-proton collisions at $\sqrt{s} = $ 13 TeV. The data corresponding to an integrated luminosity of 35.9 fb$^{-1}$ were recorded by the CMS experiment at the LHC. Events containing an isolated muon or electron and two jets, of which one is b tagged, in the final state are used in the study. From the inclusive measurement the top quark mass is found to be 172.13$^{+0.76}_{-0.77}$ GeV, where the uncertainty includes both the statistical and systematic components. The masses of the top quark and antiquark are separately determined as 172.62$^{+1.04}_{-0.75}$ and 171.79$^{+1.44}_{-1.51}$ GeV, respectively. These quantities are used to determine the mass ratio of the top antiquark to top quark of 0.9952$^{+0.0079}_{-0.0104}$, along with the difference between the top quark and antiquark masses of 0.83$^{+1.79}_{-1.35}$ GeV, both for the first time in single top quark production. The obtained mass ratio and difference agree with unity and zero, respectively, within the uncertainties, and are consistent with the conservation of CPT symmetry. This is the first measurement of the top quark mass in this particular final state to achieve a sub-GeV precision. |
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