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CMS-TOP-23-008 ; CERN-EP-2024-184
Measurement of inclusive and differential cross sections of single top quark production in association with a W boson in proton-proton collisions at $ \sqrt{s}=$ 13.6 TeV
Submitted to J. High Energy Phys.
Abstract: The first measurement of the inclusive and normalised differential cross sections of single top quark production in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13.6 TeV is presented. The data were recorded with the CMS detector at the LHC in 2022, and correspond to an integrated luminosity of 34.7 fb$^{-1}$. The analysed events contain one muon and one electron in the final state. For the inclusive measurement, multivariate discriminants exploiting the kinematic properties of the events are used to separate the signal from the dominant top quark-antiquark production background. A cross section of 82.3 $ \pm $ 2.1 (stat) $ \,^{+9.9}_{-9.7} $ (syst) $ \pm $ 3.3 (lumi) pb is obtained, consistent with the predictions of the standard model. A fiducial region is defined according to the detector acceptance to perform the differential measurements. The resulting differential distributions are unfolded to particle level and show good agreement with the predictions at next-to-leading order in perturbative quantum chromodynamics.
Figures & Tables Summary References CMS Publications
Figures

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Figure 1:
Leading-order Feynman diagrams of single top quark production in the $ \mathrm{t}\mathrm{W} $ mode. The charge-conjugate modes are implicitly included.

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Figure 1-a:
Leading-order Feynman diagrams of single top quark production in the $ \mathrm{t}\mathrm{W} $ mode. The charge-conjugate modes are implicitly included.

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Figure 1-b:
Leading-order Feynman diagrams of single top quark production in the $ \mathrm{t}\mathrm{W} $ mode. The charge-conjugate modes are implicitly included.

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Figure 2:
Representative Feynman diagrams for $ \mathrm{t}\mathrm{W} $ single top quark production at NLO that are removed from the signal definition in the DR scheme. The charge-conjugate modes are implicitly included.

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Figure 2-a:
Representative Feynman diagrams for $ \mathrm{t}\mathrm{W} $ single top quark production at NLO that are removed from the signal definition in the DR scheme. The charge-conjugate modes are implicitly included.

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Figure 2-b:
Representative Feynman diagrams for $ \mathrm{t}\mathrm{W} $ single top quark production at NLO that are removed from the signal definition in the DR scheme. The charge-conjugate modes are implicitly included.

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Figure 2-c:
Representative Feynman diagrams for $ \mathrm{t}\mathrm{W} $ single top quark production at NLO that are removed from the signal definition in the DR scheme. The charge-conjugate modes are implicitly included.

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Figure 3:
Left: the number of events observed in data (points) and predicted from simulation (filled histograms) in the $ \mathrm{e}^\pm\mu^\mp $ final state as a function of the number of jets and b-tagged jets before the maximum likelihood fit. Right: the number of loose jets per event in the $ \mathrm{e}^\pm\mu^\mp $ final state from the \njnb11 region before the maximum likelihood fit. The vertical bars on the points show the statistical uncertainties in the data. The hatched band represents the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of data to the sum of the expected yields.

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Figure 3-a:
Left: the number of events observed in data (points) and predicted from simulation (filled histograms) in the $ \mathrm{e}^\pm\mu^\mp $ final state as a function of the number of jets and b-tagged jets before the maximum likelihood fit. Right: the number of loose jets per event in the $ \mathrm{e}^\pm\mu^\mp $ final state from the \njnb11 region before the maximum likelihood fit. The vertical bars on the points show the statistical uncertainties in the data. The hatched band represents the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of data to the sum of the expected yields.

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Figure 3-b:
Left: the number of events observed in data (points) and predicted from simulation (filled histograms) in the $ \mathrm{e}^\pm\mu^\mp $ final state as a function of the number of jets and b-tagged jets before the maximum likelihood fit. Right: the number of loose jets per event in the $ \mathrm{e}^\pm\mu^\mp $ final state from the \njnb11 region before the maximum likelihood fit. The vertical bars on the points show the statistical uncertainties in the data. The hatched band represents the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of data to the sum of the expected yields.

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Figure 4:
Distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the four most discriminating variables used for the RF training of the \njnb11 region: (upper left) the $ p_{\mathrm{T}} $ of the leading loose jet; (upper right) the $ p_{\mathrm{T}} $ of the leading lepton; (lower left) the magnitude of the transverse momentum of the dilepton+jet system; and (lower right) the invariant mass of the dilepton system. The last bin of each distribution includes the overflow events, except for the leading loose jet $ p_{\mathrm{T}} $ distribution, which is only defined up to 30 GeV. The first bin in the upper left plot contains events with no loose jets. The vertical bars on the points give the statistical uncertainty in the data, and the hatched band represents the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC predictions.

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Figure 4-a:
Distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the four most discriminating variables used for the RF training of the \njnb11 region: (upper left) the $ p_{\mathrm{T}} $ of the leading loose jet; (upper right) the $ p_{\mathrm{T}} $ of the leading lepton; (lower left) the magnitude of the transverse momentum of the dilepton+jet system; and (lower right) the invariant mass of the dilepton system. The last bin of each distribution includes the overflow events, except for the leading loose jet $ p_{\mathrm{T}} $ distribution, which is only defined up to 30 GeV. The first bin in the upper left plot contains events with no loose jets. The vertical bars on the points give the statistical uncertainty in the data, and the hatched band represents the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC predictions.

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Figure 4-b:
Distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the four most discriminating variables used for the RF training of the \njnb11 region: (upper left) the $ p_{\mathrm{T}} $ of the leading loose jet; (upper right) the $ p_{\mathrm{T}} $ of the leading lepton; (lower left) the magnitude of the transverse momentum of the dilepton+jet system; and (lower right) the invariant mass of the dilepton system. The last bin of each distribution includes the overflow events, except for the leading loose jet $ p_{\mathrm{T}} $ distribution, which is only defined up to 30 GeV. The first bin in the upper left plot contains events with no loose jets. The vertical bars on the points give the statistical uncertainty in the data, and the hatched band represents the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC predictions.

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Figure 4-c:
Distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the four most discriminating variables used for the RF training of the \njnb11 region: (upper left) the $ p_{\mathrm{T}} $ of the leading loose jet; (upper right) the $ p_{\mathrm{T}} $ of the leading lepton; (lower left) the magnitude of the transverse momentum of the dilepton+jet system; and (lower right) the invariant mass of the dilepton system. The last bin of each distribution includes the overflow events, except for the leading loose jet $ p_{\mathrm{T}} $ distribution, which is only defined up to 30 GeV. The first bin in the upper left plot contains events with no loose jets. The vertical bars on the points give the statistical uncertainty in the data, and the hatched band represents the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC predictions.

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Figure 4-d:
Distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the four most discriminating variables used for the RF training of the \njnb11 region: (upper left) the $ p_{\mathrm{T}} $ of the leading loose jet; (upper right) the $ p_{\mathrm{T}} $ of the leading lepton; (lower left) the magnitude of the transverse momentum of the dilepton+jet system; and (lower right) the invariant mass of the dilepton system. The last bin of each distribution includes the overflow events, except for the leading loose jet $ p_{\mathrm{T}} $ distribution, which is only defined up to 30 GeV. The first bin in the upper left plot contains events with no loose jets. The vertical bars on the points give the statistical uncertainty in the data, and the hatched band represents the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC predictions.

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Figure 5:
The measured distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the six observables used to measure the $ \mathrm{t}\mathrm{W} $ differential cross sections. Signal events in the \njnb11 region with 0 loose jets (0 $ \mathrm{j}_{\text{l}} $) are selected. The last bin of each distribution contains the overflow events. The vertical bars on the data show the statistical uncertainty. The hatched band displays the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC expectations.

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Figure 5-a:
The measured distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the six observables used to measure the $ \mathrm{t}\mathrm{W} $ differential cross sections. Signal events in the \njnb11 region with 0 loose jets (0 $ \mathrm{j}_{\text{l}} $) are selected. The last bin of each distribution contains the overflow events. The vertical bars on the data show the statistical uncertainty. The hatched band displays the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC expectations.

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Figure 5-b:
The measured distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the six observables used to measure the $ \mathrm{t}\mathrm{W} $ differential cross sections. Signal events in the \njnb11 region with 0 loose jets (0 $ \mathrm{j}_{\text{l}} $) are selected. The last bin of each distribution contains the overflow events. The vertical bars on the data show the statistical uncertainty. The hatched band displays the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC expectations.

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Figure 5-c:
The measured distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the six observables used to measure the $ \mathrm{t}\mathrm{W} $ differential cross sections. Signal events in the \njnb11 region with 0 loose jets (0 $ \mathrm{j}_{\text{l}} $) are selected. The last bin of each distribution contains the overflow events. The vertical bars on the data show the statistical uncertainty. The hatched band displays the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC expectations.

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Figure 5-d:
The measured distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the six observables used to measure the $ \mathrm{t}\mathrm{W} $ differential cross sections. Signal events in the \njnb11 region with 0 loose jets (0 $ \mathrm{j}_{\text{l}} $) are selected. The last bin of each distribution contains the overflow events. The vertical bars on the data show the statistical uncertainty. The hatched band displays the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC expectations.

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Figure 5-e:
The measured distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the six observables used to measure the $ \mathrm{t}\mathrm{W} $ differential cross sections. Signal events in the \njnb11 region with 0 loose jets (0 $ \mathrm{j}_{\text{l}} $) are selected. The last bin of each distribution contains the overflow events. The vertical bars on the data show the statistical uncertainty. The hatched band displays the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC expectations.

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Figure 5-f:
The measured distributions from data (points) and MC simulations (filled histograms) before the maximum likelihood fit of the six observables used to measure the $ \mathrm{t}\mathrm{W} $ differential cross sections. Signal events in the \njnb11 region with 0 loose jets (0 $ \mathrm{j}_{\text{l}} $) are selected. The last bin of each distribution contains the overflow events. The vertical bars on the data show the statistical uncertainty. The hatched band displays the sum of the statistical and systematic uncertainties in the MC predictions. The lower panels show the ratio of the data to the sum of the MC expectations.

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Figure 6:
The distributions of the RF outputs for events in the \njnb11 (upper left) and \njnb21 (upper right) regions, and the subleading jet $ p_{\mathrm{T}} $ for the \njnb22 region (lower). The number of observed events (points) and estimated signal and background events (filled histograms) from the maximum likelihood fit are shown. The last bin of the subleading jet $ p_{\mathrm{T}} $ distribution includes the overflow events. The vertical bars on the points represent the statistical uncertainty in the data, and the hatched band the total uncertainty in the estimated events after the fit. The lower panels display the ratio of the data to the sum of the estimated events (points) after the fit, with the bands giving the corresponding uncertainties.

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Figure 6-a:
The distributions of the RF outputs for events in the \njnb11 (upper left) and \njnb21 (upper right) regions, and the subleading jet $ p_{\mathrm{T}} $ for the \njnb22 region (lower). The number of observed events (points) and estimated signal and background events (filled histograms) from the maximum likelihood fit are shown. The last bin of the subleading jet $ p_{\mathrm{T}} $ distribution includes the overflow events. The vertical bars on the points represent the statistical uncertainty in the data, and the hatched band the total uncertainty in the estimated events after the fit. The lower panels display the ratio of the data to the sum of the estimated events (points) after the fit, with the bands giving the corresponding uncertainties.

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Figure 6-b:
The distributions of the RF outputs for events in the \njnb11 (upper left) and \njnb21 (upper right) regions, and the subleading jet $ p_{\mathrm{T}} $ for the \njnb22 region (lower). The number of observed events (points) and estimated signal and background events (filled histograms) from the maximum likelihood fit are shown. The last bin of the subleading jet $ p_{\mathrm{T}} $ distribution includes the overflow events. The vertical bars on the points represent the statistical uncertainty in the data, and the hatched band the total uncertainty in the estimated events after the fit. The lower panels display the ratio of the data to the sum of the estimated events (points) after the fit, with the bands giving the corresponding uncertainties.

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Figure 6-c:
The distributions of the RF outputs for events in the \njnb11 (upper left) and \njnb21 (upper right) regions, and the subleading jet $ p_{\mathrm{T}} $ for the \njnb22 region (lower). The number of observed events (points) and estimated signal and background events (filled histograms) from the maximum likelihood fit are shown. The last bin of the subleading jet $ p_{\mathrm{T}} $ distribution includes the overflow events. The vertical bars on the points represent the statistical uncertainty in the data, and the hatched band the total uncertainty in the estimated events after the fit. The lower panels display the ratio of the data to the sum of the estimated events (points) after the fit, with the bands giving the corresponding uncertainties.

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Figure 7:
The $ \mathrm{t}\mathrm{W} $ cross section as a function of $ \sqrt{s} $, as obtained in this analysis (red filled circle) and in previous measurements by the CMS experiment [22,4,27,30] (black markers), with vertical bars on the markers indicating the total uncertainty in the measurements. Points corresponding to measurements at the same $ \sqrt{s} $ are horizontally shifted for better visibility. The SM prediction [15,17,16] is shown with a black line and blue uncertainty bands.

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Figure 8:
The twenty largest impacts $ \Delta\hat{\mu} $ (right column) and fit constraints $ (\hat{\theta}-\theta_0)/\Delta\theta $ (middle column) of the nuisance parameters listed in the left column from the maximum likelihood fit used to determine the inclusive $ \mathrm{t}\mathrm{W} $ cross section. The horizontal bars on the fit constraints show the ratio of the uncertainties of the fit result to the previous ones, effectively giving the constraint on the nuisance parameter. If the period is specified alongside the uncertainty name, it indicates that this is the component of the uncertainty uncorrelated by periods. There are two possible periods, before (2022PreEE) and after (2022PostEE) ECAL water leak. The JES uncertainties are divided into several sources, where $``JES - absolute''$ groups contributions from scale corrections in the barrel, pileup corrections, and initial- and final-state radiation corrections; $``JES - relative sample''$ encodes the uncertainty in the $ \eta $-dependent calibration of the jets; $``JES - relativeBal''$ accounts for the full difference between log-linear fits of MPF (Missing transverse energy Projection Fraction) and $ p_{\mathrm{T}} $ balance methods [113]; and $``JES - quark/gluon''$ comes from the corrections applied to correct the different detector response to gluon and quark jets. This last uncertainty is split in three components. These components are: light for the gluon and up, down, and strange quark jets, charm for the c jets, and bottom for the b jets.

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Figure 9:
Normalised fiducial differential $ \mathrm{t}\mathrm{W} $ production cross sections as functions of the $ p_{\mathrm{T}} $ of the leading lepton (upper left), $ p_z(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (upper right), $ p_{\mathrm{T}} $ of the jet (middle left), $ m(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (middle right), $ \Delta\varphi(\mathrm{e}^\pm,\mu^\mp) $ (lower left), and $ m_{\mathrm{T}}(\mathrm{e}^\pm,\mu^\mp,\mathrm{j},{\vec p}_{\mathrm{T}}^{\kern1pt\text{miss}}) $ (lower right). The horizontal bars on the points show the bin width. Predictions from POWHEG (PH) DR and DS + PYTHIA8 (P8), POWHEG DR + HERWIG 7 (H7), MadGraph-5\_aMC@NLO (aMC) DR, DR2, DS, and DS with a dynamic factor + PYTHIA8 are also shown. The grey band represents the statistical uncertainty and the yellow band the total uncertainty. In the lower panels, the ratio of the predictions to the data is shown.

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Figure 9-a:
Normalised fiducial differential $ \mathrm{t}\mathrm{W} $ production cross sections as functions of the $ p_{\mathrm{T}} $ of the leading lepton (upper left), $ p_z(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (upper right), $ p_{\mathrm{T}} $ of the jet (middle left), $ m(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (middle right), $ \Delta\varphi(\mathrm{e}^\pm,\mu^\mp) $ (lower left), and $ m_{\mathrm{T}}(\mathrm{e}^\pm,\mu^\mp,\mathrm{j},{\vec p}_{\mathrm{T}}^{\kern1pt\text{miss}}) $ (lower right). The horizontal bars on the points show the bin width. Predictions from POWHEG (PH) DR and DS + PYTHIA8 (P8), POWHEG DR + HERWIG 7 (H7), MadGraph-5\_aMC@NLO (aMC) DR, DR2, DS, and DS with a dynamic factor + PYTHIA8 are also shown. The grey band represents the statistical uncertainty and the yellow band the total uncertainty. In the lower panels, the ratio of the predictions to the data is shown.

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Figure 9-b:
Normalised fiducial differential $ \mathrm{t}\mathrm{W} $ production cross sections as functions of the $ p_{\mathrm{T}} $ of the leading lepton (upper left), $ p_z(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (upper right), $ p_{\mathrm{T}} $ of the jet (middle left), $ m(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (middle right), $ \Delta\varphi(\mathrm{e}^\pm,\mu^\mp) $ (lower left), and $ m_{\mathrm{T}}(\mathrm{e}^\pm,\mu^\mp,\mathrm{j},{\vec p}_{\mathrm{T}}^{\kern1pt\text{miss}}) $ (lower right). The horizontal bars on the points show the bin width. Predictions from POWHEG (PH) DR and DS + PYTHIA8 (P8), POWHEG DR + HERWIG 7 (H7), MadGraph-5\_aMC@NLO (aMC) DR, DR2, DS, and DS with a dynamic factor + PYTHIA8 are also shown. The grey band represents the statistical uncertainty and the yellow band the total uncertainty. In the lower panels, the ratio of the predictions to the data is shown.

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Figure 9-c:
Normalised fiducial differential $ \mathrm{t}\mathrm{W} $ production cross sections as functions of the $ p_{\mathrm{T}} $ of the leading lepton (upper left), $ p_z(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (upper right), $ p_{\mathrm{T}} $ of the jet (middle left), $ m(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (middle right), $ \Delta\varphi(\mathrm{e}^\pm,\mu^\mp) $ (lower left), and $ m_{\mathrm{T}}(\mathrm{e}^\pm,\mu^\mp,\mathrm{j},{\vec p}_{\mathrm{T}}^{\kern1pt\text{miss}}) $ (lower right). The horizontal bars on the points show the bin width. Predictions from POWHEG (PH) DR and DS + PYTHIA8 (P8), POWHEG DR + HERWIG 7 (H7), MadGraph-5\_aMC@NLO (aMC) DR, DR2, DS, and DS with a dynamic factor + PYTHIA8 are also shown. The grey band represents the statistical uncertainty and the yellow band the total uncertainty. In the lower panels, the ratio of the predictions to the data is shown.

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Figure 9-d:
Normalised fiducial differential $ \mathrm{t}\mathrm{W} $ production cross sections as functions of the $ p_{\mathrm{T}} $ of the leading lepton (upper left), $ p_z(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (upper right), $ p_{\mathrm{T}} $ of the jet (middle left), $ m(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (middle right), $ \Delta\varphi(\mathrm{e}^\pm,\mu^\mp) $ (lower left), and $ m_{\mathrm{T}}(\mathrm{e}^\pm,\mu^\mp,\mathrm{j},{\vec p}_{\mathrm{T}}^{\kern1pt\text{miss}}) $ (lower right). The horizontal bars on the points show the bin width. Predictions from POWHEG (PH) DR and DS + PYTHIA8 (P8), POWHEG DR + HERWIG 7 (H7), MadGraph-5\_aMC@NLO (aMC) DR, DR2, DS, and DS with a dynamic factor + PYTHIA8 are also shown. The grey band represents the statistical uncertainty and the yellow band the total uncertainty. In the lower panels, the ratio of the predictions to the data is shown.

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Figure 9-e:
Normalised fiducial differential $ \mathrm{t}\mathrm{W} $ production cross sections as functions of the $ p_{\mathrm{T}} $ of the leading lepton (upper left), $ p_z(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (upper right), $ p_{\mathrm{T}} $ of the jet (middle left), $ m(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (middle right), $ \Delta\varphi(\mathrm{e}^\pm,\mu^\mp) $ (lower left), and $ m_{\mathrm{T}}(\mathrm{e}^\pm,\mu^\mp,\mathrm{j},{\vec p}_{\mathrm{T}}^{\kern1pt\text{miss}}) $ (lower right). The horizontal bars on the points show the bin width. Predictions from POWHEG (PH) DR and DS + PYTHIA8 (P8), POWHEG DR + HERWIG 7 (H7), MadGraph-5\_aMC@NLO (aMC) DR, DR2, DS, and DS with a dynamic factor + PYTHIA8 are also shown. The grey band represents the statistical uncertainty and the yellow band the total uncertainty. In the lower panels, the ratio of the predictions to the data is shown.

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Figure 9-f:
Normalised fiducial differential $ \mathrm{t}\mathrm{W} $ production cross sections as functions of the $ p_{\mathrm{T}} $ of the leading lepton (upper left), $ p_z(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (upper right), $ p_{\mathrm{T}} $ of the jet (middle left), $ m(\mathrm{e}^\pm,\mu^\mp,\mathrm{j}) $ (middle right), $ \Delta\varphi(\mathrm{e}^\pm,\mu^\mp) $ (lower left), and $ m_{\mathrm{T}}(\mathrm{e}^\pm,\mu^\mp,\mathrm{j},{\vec p}_{\mathrm{T}}^{\kern1pt\text{miss}}) $ (lower right). The horizontal bars on the points show the bin width. Predictions from POWHEG (PH) DR and DS + PYTHIA8 (P8), POWHEG DR + HERWIG 7 (H7), MadGraph-5\_aMC@NLO (aMC) DR, DR2, DS, and DS with a dynamic factor + PYTHIA8 are also shown. The grey band represents the statistical uncertainty and the yellow band the total uncertainty. In the lower panels, the ratio of the predictions to the data is shown.
Tables

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Table 1:
Selection requirements for particle-level objects.

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Table 2:
Definition of the fiducial region.

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Table 3:
The number of estimated signal and background events after the fit in the \njnb11, \njnb21, and \njnb22 regions compared to the observed number of events. The total uncertainties in the estimated events after the fit are given.

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Table 4:
The $ p $-values from the $ \chi^2 $ goodness-of-fit tests comparing the six differential cross section measurements with the predictions from POWHEG (PH) DR and DS + PYTHIA8 (P8) and POWHEG DR + HERWIG 7 (H7). The complete covariance matrix from the results and the statistical uncertainties in the predictions are taken into account.

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Table 5:
The $ p $-values from the $ \chi^2 $ goodness-of-fit tests comparing the six differential cross section measurements with the predictions from MadGraph-5\_aMC@NLO (aMC) DR, DR2, DS, and DS with a dynamic factor + PYTHIA8. The complete covariance matrix from the results and the statistical uncertainties in the predictions are taken into account.
Summary
Inclusive and normalised differential cross sections of top quark production in association with a W boson are measured in proton-proton collision data at $ \sqrt{s}=$ 13.6 TeV. The selected data, corresponding to an integrated luminosity of 34.7 fb$^{-1}$, contain events with an electron and a muon of opposite charge. For the inclusive measurement, the events have been categorised depending on the number of jets and jets originating from the fragmentation of bottom quarks. The signal is measured using a maximum likelihood fit to the distribution of random forest discriminants in the regions with one or two jets where one of them is identified as originating from the fragmentation of a bottom quark (b jet), and to the transverse momentum ($ p_{\mathrm{T}} $) distribution of the second-highest $ p_{\mathrm{T}} $ jet in a third category with two jets, both of which are b jets. The measured inclusive cross section is 82.3 $ \pm $ 2.1 (stat) $ \,^{+9.9}_{-9.7} $ (syst) $ \pm $ 3.3 (lumi) pb, with a total relative uncertainty of about 13%. This measurement is in agreement with the latest theoretical prediction at approximate next-to-next-to-next-to-leading order accuracy in perturbative quantum chromodynamics and with other measurements. The differential cross section measurements are performed as functions of six kinematic observables of the events in the fiducial phase space corresponding to the selection criteria. The results have relative uncertainties in the range of 20--40%, depending on the measured observable. The uncertainties are mainly statistical. There is good agreement between the measurements and the predictions from the different event generators. The different approaches used to simulate $ \mathrm{t}\mathrm{W} $ events give similar values in all distributions, which points to small effects related to the $ \mathrm{t}\mathrm{W} $/ $ \mathrm{t} \overline{\mathrm{t}} $ interference on these distributions in the defined fiducial region.
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Compact Muon Solenoid
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