Date

Version 2
Measurements of the production cross-section for a $Z$ boson in association with $b$- or $c$-jets in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Aakvaag, Erlend ; Abbott, Braden Keim ; et al.
Eur.Phys.J.C 84 (2024) 984, 2024.
Inspire Record 2771257 DOI 10.17182/hepdata.151815

This paper presents a measurement of the production cross-section of a $Z$ boson in association with $b$- or $c$-jets, in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb$^{-1}$. Inclusive and differential cross-sections are measured for events containing a $Z$ boson decaying into electrons or muons and produced in association with at least one $b$-jet, at least one $c$-jet, or at least two $b$-jets with transverse momentum $p_\textrm{T} > 20$ GeV and rapidity $|y| < 2.5$. Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected $Z + \ge 1 c$-jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions.

29 data tables

Figure 6(left) of the article. Measured fiducial cross sections for events with $Z \left( \rightarrow \ell \ell \right) \geq 1 b$-jet. The thin inner band corresponds to the statistical uncertainty of the data, and the outer band to statistical and systematic uncertainties of the data, added in quadrature.

Figure 6(right) of the article. Measured fiducial cross sections for events with $Z \left( \rightarrow \ell \ell \right) \geq 2 b$-jets. The thin inner band corresponds to the statistical uncertainty of the data, and the outer band to statistical and systematic uncertainties of the data, added in quadrature.

Figure 7 of the article. Measured fiducial cross sections for events with $Z \left( \rightarrow \ell \ell \right) \geq 1 c$-jet. The thin inner band corresponds to the statistical uncertainty of the data, and the outer band to statistical and systematic uncertainties of the data, added in quadrature.

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Search for $t\bar{t}H/A \rightarrow t\bar{t}t\bar{t}$ production in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Aakvaag, Erlend ; Abbott, Braden Keim ; et al.
Eur.Phys.J.C 85 (2025) 573, 2025.
Inspire Record 2823281 DOI 10.17182/hepdata.158356

A search is presented for a heavy scalar ($H$) or pseudo-scalar ($A$) predicted by the two-Higgs-doublet models, where the $H/A$ is produced in association with a top-quark pair ($t\bar{t}H/A$), and with the $H/A$ decaying into a $t\bar{t}$ pair. Events are selected requiring exactly one or two opposite-charge electrons or muons. Data-driven corrections are applied to improve the modelling of the $t\bar{t}$+jets background in the regime with high jet and $b$-jet multiplicities. These include a novel multi-dimensional kinematic reweighting based on a neural network trained using data and simulations. An $H/A$-mass parameterised graph neural network is trained to optimise the signal-to-background discrimination. In combination with the previous search performed by the ATLAS Collaboration in the multilepton final state, the observed upper limits on the $t\bar{t}H/A \rightarrow t\bar{t}t\bar{t}$ production cross-section at 95% confidence level range between 14 fb and 5.0 fb for an $H/A$ with mass between 400 GeV and 1000 GeV, respectively. Assuming that both the $H$ and $A$ contribute to the $t\bar{t}t\bar{t}$ cross-section, $\tan\beta$ values below 1.7 or 0.7 are excluded for a mass of 400 GeV or 1000 GeV, respectively. The results are also used to constrain a model predicting the pair production of a colour-octet scalar, with the scalar decaying into a $t\bar{t}$ pair.

23 data tables

Post-fit distribution of the GNN score evaluated with $m_{H/A}$ = 400 GeV in the 1L region with $\geq 10$ jets and four $b$-tagged jets. The fit is performed under the background-only hypothesis.

Post-fit distribution of the GNN score evaluated with $m_{H/A}$ = 400 GeV in the 2LOS region with $\geq8$ jets and $\geq 4$ $𝑏$-tagged jets. The fit is performed under the background-only hypothesis.

Post-fit distribution of the GNN score evaluated with $m_{H/A}$ = 400 GeV in the validation region in the 1L region with $\geq 10$ jets. These regions do not enter the fit. The post-fit background prediction is obtained using the post-fit nuisance parameters from the background-only fit in the control and signal regions.

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Search for low-mass resonances decaying into two jets and produced in association with a photon or a jet at $\sqrt{s}=13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Aakvaag, Erlend ; Abbott, Braden Keim ; et al.
Phys.Rev.D 110 (2024) 032002, 2024.
Inspire Record 2768375 DOI 10.17182/hepdata.145799

A search is performed for localized excesses in the low-mass dijet invariant mass distribution, targeting a hypothetical new particle decaying into two jets and produced in association with either a high transverse momentum photon or a jet. The search uses the full Run 2 data sample from LHC proton-proton collisions collected by the ATLAS experiment at a center-of-mass energy of 13 TeV during 2015-2018. Two variants of the search are presented for each type of initial-state radiation: one that makes no jet flavor requirements and one that requires both of the jets to have been identified as containing $b$-hadrons. No excess is observed relative to the Standard Model prediction, and the data are used to set upper limits on the production cross-section for a benchmark $Z'$ model and, separately, for generic, beyond the Standard Model scenarios which might produce a Gaussian-shaped contribution to dijet invariant mass distributions. The results extend the current constraints on dijet resonances to the mass range between 200 and 650 GeV.

12 data tables

Dijet invariant mass distributions data compared to the fitted background estimates for the $\gamma j j$ channel. The distributions are shown here with the $m_{jj}$ resolution binning.

Dijet invariant mass distributions data compared to the fitted background estimates for the $\gamma b b$ channel. The distributions are shown here with the $m_{jj}$ resolution binning.

Dijet invariant mass distributions data compared to the fitted background estimates for the $j j j$ channel. The distributions are shown here with the $m_{jj}$ resolution binning.

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Search for a new scalar decaying into new spin-1 bosons in four-lepton final states with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
Phys.Lett.B 865 (2025) 139472, 2025.
Inspire Record 2842018 DOI 10.17182/hepdata.145171

A search is conducted for a new scalar boson $S$, with a mass distinct from that of the Higgs boson, decaying into four leptons ($\ell =$$e$, $\mu$) via an intermediate state containing two on-shell, promptly decaying new spin-1 bosons $Z_\text{d}$: $S \rightarrow Z_\text{d}Z_\text{d} \rightarrow 4\ell$, where the $Z_\text{d}$ boson has a mass between 15 and 300 GeV, and the $S$ boson has a mass between either 30 and 115 GeV or 130 and 800 GeV. The search uses proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider with an integrated luminosity of 139 fb$^{-1}$ at a centre-of-mass energy of $\sqrt{s}=13$ TeV. No significant excess above the Standard Model background expectation is observed. Upper limits at 95% confidence level are set on the production cross-section times branching ratio, $\sigma(gg \to S) \times \mathcal{B}(S\rightarrow Z_\text{d}Z_\text{d} \rightarrow 4\ell)$, as a function of the mass of both particles, $m_S$ and $m_{Z\text{d}}$.

32 data tables

Average dilepton mass distribution $\left\langle m_{\ell\ell}\right\rangle = \frac{1}{2}\left(m_{ab} + m_{cd}\right)$ in Signal Region 1.

Average dilepton mass distribution $\left\langle m_{\ell\ell}\right\rangle = \frac{1}{2}\left(m_{ab} + m_{cd}\right)$ in Signal Region 2.

Total invariant mass distribution $m_{4\ell}$ in Signal Region 1.

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Version 2
Search for nonresonant pair production of Higgs bosons in the $b\bar{b}b\bar{b}$ final state in $pp$ collisions at $\sqrt{s}= 13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
Phys.Rev.D 108 (2023) 052003, 2023.
Inspire Record 2621476 DOI 10.17182/hepdata.137769

A search for nonresonant Higgs boson pair production in the $b\bar{b}b\bar{b}$ final state is presented. The analysis uses 126 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}={13}$ TeV collected with the ATLAS detector at the Large Hadron Collider, and targets both the gluon-gluon fusion and vector-boson fusion production modes. No evidence of the signal is found and the observed (expected) upper limit on the cross-section for nonresonant Higgs boson pair production is determined to be 5.4 (8.1) times the Standard Model predicted cross-section at 95% confidence level. Constraints are placed on modifiers to the $HHH$ and $HHVV$ couplings. The observed (expected) $2\sigma$ constraints on the $HHH$ coupling modifier, $\kappa_\lambda$, are determined to be $[-3.5, 11.3]$ ($[-5.4, 11.4]$), while the corresponding constraints for the $HHVV$ coupling modifier, $\kappa_{2V}$, are $[-0.0, 2.1]$ ($[-0.1, 2.1]$). In addition, constraints on relevant coefficients are derived in the context of the Standard Model effective field theory and Higgs effective field theory, and upper limits on the $HH$ production cross-section are placed in seven Higgs effective field theory benchmark scenarios.

38 data tables

Distributions of the reconstructed m<sub>HH</sub> in data (shown by the black points), the estimated background (shown by the yellow histograms) in the VBF signal region with |&Delta;&eta;<sub>HH</sub>| &lt; 1.5. The hatching shows the total uncertainty of the background estimate. The distribution of the expected background is obtained using the best-fit values of the nuisance parameters in the fit to the data with the background-only hypothesis. Distributions for three choices of couplings are shown: the SM, &kappa;<sub>&lambda;</sub>= 6, and &kappa;<sub>2V</sub> = 0 (with all other couplings set to their SM values in the last two models), scaled so as to be visible on the plot. The lower panels show the ratio of the observed data yield to the predicted background in each bin. Events in the overflow bins are counted in the yields of the final bins. In the HEPData entry, the raw value per histogram bin is provided, while in the published paper the values in the histogram are scaled by the bin width.

Distributions of the reconstructed m<sub>HH</sub> in data (shown by the black points), the estimated background (shown by the yellow histograms) in the VBF signal region with |&Delta;&eta;<sub>HH</sub>| &gt; 1.5. The hatching shows the total uncertainty of the background estimate. The distribution of the expected background is obtained using the best-fit values of the nuisance parameters in the fit to the data with the background-only hypothesis. Distributions for three choices of couplings are shown: the SM, &kappa;<sub>&lambda;</sub>= 6, and &kappa;<sub>2V</sub> = 0 (with all other couplings set to their SM values in the last two models), scaled so as to be visible on the plot. The lower panels show the ratio of the observed data yield to the predicted background in each bin. Events in the overflow bins are counted in the yields of the final bins. In the HEPData entry, the raw value per histogram bin is provided, while in the published paper the values in the histogram are scaled by the bin width.

The observed 95&#37; CL exclusion limits as a function of &kappa;<sub>&lambda;</sub> (obtained using the signal strength &mu;<sub>ggF+VBF</sub> as the POI) from the combined ggF and VBF signal regions, as shown by the solid black line. The value of &kappa;<sub>2V</sub> is fixed to 1. The blue and yellow bands show respectively the 1&sigma; and 2&sigma; bands around the expected exclusion limits, which are shown by the dashed black line. The expected exclusion limits are obtained using a fit to the data with the background-only hypothesis. The dark red line shows the predicted combined ggF and VBF HH cross-section as a function of &kappa;<sub>&lambda;</sub>.

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Search for high-mass resonances in final states with a $\tau$-lepton and missing transverse momentum with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Dale ; et al.
Phys.Rev.D 109 (2024) 112008, 2024.
Inspire Record 2762382 DOI 10.17182/hepdata.146026

A search for high-mass resonances decaying into a $\tau$-lepton and a neutrino using proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV is presented. The full Run 2 data sample corresponding to an integrated luminosity of 139 fb$^{-1}$ recorded by the ATLAS experiment in the years 2015-2018 is analyzed. The $\tau$-lepton is reconstructed in its hadronic decay modes and the total transverse momentum carried out by neutrinos is inferred from the reconstructed missing transverse momentum. The search for new physics is performed on the transverse mass between the $\tau$-lepton and the missing transverse momentum. No excess of events above the Standard Model expectation is observed and upper exclusion limits are set on the $W^\prime\to \tau \nu$ production cross-section. Heavy $W^\prime$ vector bosons with masses up to 5.0 TeV are excluded at 95% confidence level, assuming that they have the same couplings as the Standard Model $W$ boson. For non-universal couplings, $W^\prime$ bosons are excluded for masses less than 3.5-5.0 TeV, depending on the model parameters. In addition, model-independent limits on the visible cross-section times branching ratio are determined as a function of the lower threshold on the transverse mass of the $\tau$-lepton and missing transverse momentum.

8 data tables

Observed and predicted $m_{\rm T}$ distributions including SSM and NU (cot$\theta$ = 5.5) $W^{\prime}$ signals with masses of 4 TeV. Please note that in the paper figure the bin content is divided by the bin width, but this is not done in the HepData table.

Observed and expected 95% CL upper limits on cross section times $\tau\nu$ branching fraction for $W^{\prime}_{\rm SSM}$.

Regions of the non-universal parameter space excluded at 95% CL.

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Version 2
Search for new phenomena in final states with photons, jets and missing transverse momentum in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, D.C. ; et al.
JHEP 07 (2023) 021, 2023.
Inspire Record 2094882 DOI 10.17182/hepdata.115570

A search for new phenomena has been performed in final states with at least one isolated high-momentum photon, jets and missing transverse momentum in proton--proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV. The data, collected by the ATLAS experiment at the CERN LHC, correspond to an integrated luminosity of 139 $fb^{-1}$. The experimental results are interpreted in a supersymmetric model in which pair-produced gluinos decay into neutralinos, which in turn decay into a gravitino, at least one photon, and jets. No significant deviations from the predictions of the Standard Model are observed. Upper limits are set on the visible cross section due to physics beyond the Standard Model, and lower limits are set on the masses of the gluinos and neutralinos, all at 95% confidence level. Visible cross sections greater than 0.022 fb are excluded and pair-produced gluinos with masses up to 2200 GeV are excluded for most of the NLSP masses investigated.

33 data tables

The observed and expected (post-fit) yields in the control and validation regions. The lower panel shows the difference in standard deviations between the observed and expected yields, considering both the systematic and statistical uncertainties on the background expectation.

Observed (points with error bars) and expected background (solid histograms) distributions for $E_{T}^{miss}$ in the signal region (a) SRL, (b) SRM and (c) SRH after the background-only fit applied to the CRs. The predicted signal distributions for the two models with a gluino mass of 2000 GeV and neutralino mass of 250 GeV (SRL), 1050 GeV (SRM) or 1950 GeV (SRH) are also shown for comparison. The uncertainties in the SM background are only statistical.

Observed (points with error bars) and expected background (solid histograms) distributions for $E_{T}^{miss}$ in the signal region (a) SRL, (b) SRM and (c) SRH after the background-only fit applied to the CRs. The predicted signal distributions for the two models with a gluino mass of 2000 GeV and neutralino mass of 250 GeV (SRL), 1050 GeV (SRM) or 1950 GeV (SRH) are also shown for comparison. The uncertainties in the SM background are only statistical.

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Measurement of the total and differential cross-sections of $t\bar{t}W$ production in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 05 (2024) 131, 2024.
Inspire Record 2745375 DOI 10.17182/hepdata.149762

Measurements of inclusive and differential production cross-sections of a top-quark-top-antiquark pair in association with a $W$ boson ($t\bar{t}W$) are presented. They are performed by targeting final states with two same-sign or three isolated leptons (electrons or muons) and are based on $\sqrt{s}=13$ TeV proton-proton collision data with an integrated luminosity of 140 fb$^{-1}$, recorded from 2015 to 2018 with the ATLAS detector at the Large Hadron Collider. The inclusive $t\bar{t}W$ production cross-section is measured to be $880 \pm 80$ fb, compared to a reference theoretical prediction of $745 \pm 50\,\textrm{(scale)} \pm 13\,\textrm{(2-loop approx.)} \pm 19\,\textrm{(PDF,} \alpha_{\textrm{S}})$ fb. Differential cross-section measurements characterise this process in detail for the first time. Several particle-level observables are compared with a variety of theoretical predictions, which generally agree well with the normalised differential cross-section results. Additionally, the relative charge asymmetry of $t\bar{t}W^{+}$ and $t\bar{t}W^{-}$ is measured inclusively to be ${A_{\mathrm{C}}^{\mathrm{rel}}} = 0.33 \pm 0.05$, in very good agreement with the theoretical prediction of $0.322 \pm 0.003\,\mathrm{(scale)} \pm 0.007\,\mathrm{(PDF)}$, as well as differentially.

2 data tables

All the entries of this HEP data record are listed.

Results of inclusive cross section measurement


Version 2
Differential cross-sections for events with missing transverse momentum and jets measured with the ATLAS detector in 13 TeV proton-proton collisions

The ATLAS collaboration Aad, Georges ; Aakvaag, Erlend ; Abbott, Braden Keim ; et al.
JHEP 08 (2024) 223, 2024.
Inspire Record 2765017 DOI 10.17182/hepdata.149990

Measurements of inclusive, differential cross-sections for the production of events with missing transverse momentum in association with jets in proton-proton collisions at $\sqrt{s}=13~$TeV are presented. The measurements are made with the ATLAS detector using an integrated luminosity of $140~$fb$^{-1}$ and include measurements of dijet distributions in a region in which vector-boson fusion processes are enhanced. They are unfolded to correct for detector resolution and efficiency within the fiducial acceptance, and are designed to allow robust comparisons with a wide range of theoretical predictions. A measurement of differential cross sections for the $Z~\to \nu\nu$ process is made. The measurements are generally well-described by Standard Model predictions except for the dijet invariant mass distribution. Auxiliary measurements of the hadronic system recoiling against isolated leptons, and photons, are also made in the same phase space. Ratios between the measured distributions are then derived, to take advantage of cancellations in modelling effects and some of the major systematic uncertainties. These measurements are sensitive to new phenomena, and provide a mechanism to easily set constraints on phenomenological models. To illustrate the robustness of the approach, these ratios are compared with two common Dark Matter models, where the constraints derived from the measurement are comparable to those set by dedicated detector-level searches.

146 data tables

The measured $p_\text{T}^\text{miss}$ differential cross-sections in the $p_\text{T}^\text{miss}+\text{jets}$ region of the incluse jet phase space, compared with the SM predictions. The middle panels show the ratios of the predictions to the data, along with their uncertainties, while the lower panels show the relative contributions from different SM processes relative to the total MEPS@NLO prediction. Note that individually numbered PDF components ('dK_PDF_') in the uncertainty breakdown correspond to NNPDF Hessian eigenvectors. Uncertainty components labeled 'VV_dK' include Vjj processes.

The measured $p_\text{T}^\text{recoil}$ differential cross-sections in the $1\mu+\text{jets}$ region of the incluse jet phase space, compared with the SM predictions. The middle panels show the ratios of the predictions to the data, along with their uncertainties, while the lower panels show the relative contributions from different SM processes relative to the total MEPS@NLO prediction. Note that individually numbered PDF components ('dK_PDF_') in the uncertainty breakdown correspond to NNPDF Hessian eigenvectors. Uncertainty components labeled 'VV_dK' include Vjj processes.

The measured $p_\text{T}^\text{recoil}$ differential cross-sections in the $1e+\text{jets}$ region of the incluse jet phase space, compared with the SM predictions. The middle panels show the ratios of the predictions to the data, along with their uncertainties, while the lower panels show the relative contributions from different SM processes relative to the total MEPS@NLO prediction. Note that individually numbered PDF components ('dK_PDF_') in the uncertainty breakdown correspond to NNPDF Hessian eigenvectors. Uncertainty components labeled 'VV_dK' include Vjj processes.

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Search for charged-lepton-flavour violating $\mu\tau qt$ interactions in top-quark production and decay in $pp$ collisions at $\sqrt{s}= 13$ TeV with the ATLAS detector at the LHC

The ATLAS collaboration Aad, Georges ; Aakvaag, Erlend ; Abbott, Braden Keim ; et al.
Phys.Rev.D 110 (2024) 012014, 2024.
Inspire Record 2767173 DOI 10.17182/hepdata.151734

A search for charged-lepton-flavour violating $\mu\tau qt$ ($q=u,c$) interactions is presented, considering both top-quark production and decay. The data analysed correspond to 140 $\textrm{fb}^{-1}$ of proton-proton collisions at a centre-of-mass energy of $\sqrt{s}= $13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The analysis targets events containing two muons with the same electric charge, a hadronically decaying $\tau$-lepton and at least one jet, with exactly one $b$-tagged jet, produced by a $\mu\tau qt$ interaction. Agreement with the Standard Model expectation within $1.6\sigma$ is observed, and limits are set at the 95% CL on the charged-lepton-flavour violation branching ratio of $\mathcal{B}(t \to \mu\tau q) < 8.7 \times 10^{-7}$. An Effective Field Theory interpretation is performed yielding 95% CL limits on Wilson coefficients, dependent on the flavour of the associated light quark and the Lorentz structure of the coupling. These range from $|c_{\mathsf{lequ}}^{3(2313)}| / \Lambda^{2} < 0.10\textrm{ TeV}^{-2}$ for $\mu\tau ut$ to $|c_{\mathsf{ lequ}}^{1(2323)}| / \Lambda^{2} < 1.8\textrm{ TeV}^{-2}$ for $\mu\tau ct$. An additional interpretation is performed for scalar leptoquark production inducing charged lepton flavour violation, with fixed inter-generational couplings. Upper limits on leptoquark coupling strengths are set at the 95% CL, ranging from $\lambda^{\textrm{LQ}} = $1.3 to $\lambda^{\textrm{LQ}} = $3.7 for leptoquark masses between 0.5 and 2.0 TeV.

18 data tables

Observed event yields in $\textrm{CR}t\bar{t}\mu$ compared with pre-fit expectations from Monte Carlo simulations, as a function of the scalar sum of lepton and jet transverse momenta, $H_{\mathrm{T}}$. The last bin includes overflow events. `Signal (prod.)' and `Signal (dec.)' refer to the single-top-quark production and top-quark pair decay signal contributions, respectively. The pre-fit signal yield represents all Wilson coefficients set to 0.1 simultaneously for a new physics scale of $\Lambda=1$ TeV.

Observed event yields in $\textrm{CR}t\bar{t}\mu$ compared with post-fit expectations from Monte Carlo simulations, as a function of the scalar sum of lepton and jet transverse momenta, $H_{\mathrm{T}}$. The last bin includes overflow events. `Signal (prod.)' and `Signal (dec.)' refer to the single-top-quark production and top-quark pair decay signal contributions, respectively.

Observed event yields in $\textrm{SR}$ compared with pre-fit expectations from Monte Carlo simulations, as a function of the scalar sum of lepton and jet transverse momenta, $H_{\mathrm{T}}$. The last bin includes overflow events. `Signal (prod.)' and `Signal (dec.)' refer to the single-top-quark production and top-quark pair decay signal contributions, respectively. The pre-fit signal yield represents all Wilson coefficients set to 0.1 simultaneously for a new physics scale of $\Lambda=1$ TeV.

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