Measurements of differential cross-sections in four-lepton events in 13 TeV proton-proton collisions with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Brad ; et al.
JHEP 07 (2021) 005, 2021.
Inspire Record 1849535 DOI 10.17182/hepdata.94413

Measurements of four-lepton differential and integrated fiducial cross-sections in events with two same-flavour, opposite-charge electron or muon pairs are presented. The data correspond to 139 fb$^{-1}$ of $\sqrt{s}=13$ TeV proton-proton collisions, collected by the ATLAS detector during Run 2 of the Large Hadron Collider (2015-2018). The final state has contributions from a number of interesting Standard Model processes that dominate in different four-lepton invariant mass regions, including single $Z$ boson production, Higgs boson production and on-shell $ZZ$ production, with a complex mix of interference terms, and possible contributions from physics beyond the Standard Model. The differential cross-sections include the four-lepton invariant mass inclusively, in slices of other kinematic variables, and in different lepton flavour categories. Also measured are dilepton invariant masses, transverse momenta, and angular correlation variables, in four regions of four-lepton invariant mass, each dominated by different processes. The measurements are corrected for detector effects and are compared with state-of-the-art Standard Model calculations, which are found to be consistent with the data. The $Z\rightarrow 4\ell$ branching fraction is extracted, giving a value of $\left(4.41 \pm 0.30\right) \times 10^{-6}$. Constraints on effective field theory parameters and a model based on a spontaneously broken $B-L$ gauge symmetry are also evaluated. Further reinterpretations can be performed with the provided information.

65 data tables match query

Inclusive differential cross section for four leptons (Max = 1710~GeV).

Inclusive differential cross section for four muons (Max = 1320~GeV)

Inclusive differential cross section for four electrons (Max = 887~GeV).

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Search for new non-resonant phenomena in high-mass dilepton final states with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
JHEP 11 (2020) 005, 2020.
Inspire Record 1802523 DOI 10.17182/hepdata.94786

A search for new physics with non-resonant signals in dielectron and dimuon final states in the mass range above 2 TeV is presented. This is the first search for non-resonant signals in dilepton final states at the LHC to use a background estimate from the data. The data, corresponding to an integrated luminosity of 139 fb$^{-1}$, were recorded by the ATLAS experiment in proton-proton collisions at a center-of-mass energy of $\sqrt{s} = 13$ TeV during Run 2 of the Large Hadron Collider. The benchmark signal signature is a two-quark and two-lepton contact interaction, which would enhance the dilepton event rate at the TeV mass scale. To model the contribution from background processes a functional form is fit to the dilepton invariant-mass spectra in data in a mass region below the region of interest. It is then extrapolated to a high-mass signal region to obtain the expected background there. No significant deviation from the expected background is observed in the data. Upper limits at 95 % CL on the number of events and the visible cross-section times branching fraction for processes involving new physics are provided. Observed (expected) 95 % CL lower limits on the contact interaction energy scale reach 35.8 (37.6) TeV.

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Expected and observed event yields in each signal bin.

Model-independent upper limits at 95% CL on the number of signal events in the (constructive/destructive interference) SRs used in the analysis for dielectrons and dimuons.

Lower limits at 95$\%$ CL on $\Lambda$ for the dielectron channel for different signal chiralities in the (constructive/destructive interference) SRs of the analysis.

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Measurements of inclusive and differential cross-sections of combined $t\bar{t}\gamma$ and $tW\gamma$ production in the $e\mkern-2mu\mu$ channel at 13 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
JHEP 09 (2020) 049, 2020.
Inspire Record 1806806 DOI 10.17182/hepdata.94915

Inclusive and differential cross-sections for the production of top quarks in association with a photon are measured with proton$-$proton collision data corresponding to an integrated luminosity of 139 fb$^{-1}$. The data were collected by the ATLAS detector at the LHC during Run 2 between 2015 and 2018 at a centre-of-mass energy of 13 TeV. The measurements are performed in a fiducial volume defined at parton level. Events with exactly one photon, one electron and one muon of opposite sign, and at least two jets, of which at least one is $b$-tagged, are selected. The fiducial cross-section is measured to be $39.6\,^{+2.7}_{-2.3}\,\textrm{fb}$. Differential cross-sections as functions of several observables are compared with state-of-the-art Monte Carlo simulations and next-to-leading-order theoretical calculations. These include cross-sections as functions of photon kinematic variables, angular variables related to the photon and the leptons, and angular separations between the two leptons in the event. All measurements are in agreement with the predictions from the Standard Model.

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The measured fiducial cross-section in the electron-muon channel. The first uncertainty is the statistical uncertainty and the second one is the systematic uncertainty.

The absolute differential cross-section measured in the fiducial phase-space as a function of the photon pT in the electron-muon channel. The uncertainty is decomposed into four components which are the signal modelling uncertainty, the background modelling uncertainty, the experimental uncertainty, and the data statistical uncertainty.

The absolute differential cross-section measured in the fiducial phase-space as a function of the photon $|\eta|$ in the electron-muon channel. The uncertainty is decomposed into four components which are the signal modelling uncertainty, the background modelling uncertainty, the experimental uncertainty, and the data statistical uncertainty.

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Search for heavy resonances decaying into a photon and a hadronically decaying Higgs boson in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
Phys.Rev.Lett. 125 (2020) 251802, 2020.
Inspire Record 1811594 DOI 10.17182/hepdata.95538

This Letter presents a search for the production of new heavy resonances decaying into a Higgs boson and a photon using proton-proton collision data at $\sqrt{s}=13$ TeV collected by the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 139 fb$^{-1}$. The analysis is performed by reconstructing hadronically decaying Higgs boson $(H\to b\bar{b})$ candidates as single large-radius jets. A novel algorithm using information about the jet constituents in the center-of-mass frame of the jet is implemented to identify the two $b$-quarks in the single jet. No significant excess of events is observed above the expected background. Upper limits are set on the production cross-section times branching fraction for narrow spin-1 resonances decaying into a Higgs boson and a photon in the resonance mass range from 0.7 to 4 TeV, cross-sections times branching fraction are excluded between 11.6 fb and 0.11 fb at a 95% confidence level.

5 data tables match query

Data distribution of the reconstructed $m_{J\gamma}$ and background only fitting in the single-b-tagged category. Background and signal fit functions are provided in Table 3. Background event yields are calculated using the fitted background function.

Data distribution of the reconstructed $m_{J\gamma}$ and background only fitting in the double-b-tagged category. Background and signal fit functions are provided in Table 3. Background event yields are calculated using the fitted background function.

Background and signal functions, with their fit parameters. For the background function, the parameters are fitted from the data distribution. The "Yield" is the total number of events in data in the single-b-tagged or double-b-tagged fitting range. For the single-b-tagged category, the fitting range is [1400GeV, 4200GeV], and for the double-b-tagged category, it is [600GeV, 4200GeV]. The background event yields per bin in Table 1 and Table 2 are calculated using the data yield multiplied by the integral of the normalized background function in that bin. For the signal function, the value for the parameters are from parametrisation studies and CB stands for a Crystal-Ball function. Signal distributions in Figure 1a and Figure 1b are normalized to an arbitrary yield, for illustration purpose.

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Search for pairs of scalar leptoquarks decaying into quarks and electrons or muons in $\sqrt{s}=13$ TeV pp collisions with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
JHEP 10 (2020) 112, 2020.
Inspire Record 1800410 DOI 10.17182/hepdata.95211

A search for new-physics resonances decaying into a lepton and a jet performed by the ATLAS experiment is presented. Scalar leptoquarks pair-produced in $pp$ collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider are considered using an integrated luminosity of 139 fb$^{-1}$, corresponding to the full Run 2 dataset. They are searched for in events with two electrons or two muons and two or more jets, including jets identified as arising from the fragmentation of $c$- or $b$-quarks. The observed yield in each channel is consistent with the Standard Model background expectation. Leptoquarks with masses below 1.8 TeV and 1.7 TeV are excluded in the electron and muon channels, respectively, assuming a branching ratio into a charged lepton and a quark of 100%, with minimal dependence on the quark flavour. Upper limits on the aforementioned branching ratio are also given as a function of the leptoquark mass.

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Distribution of the resonance mass in the pretag Signal Region of the $ qe$ channel for the post-fit background, the observed data, and the expected signal with $m_{LQ} = 1$ TeV.

Distribution of the resonance mass in the pretag Signal Region of the $ q\mu$ channel for the post-fit background, the observed data, and the expected signal with $m_{LQ} = 1$ TeV.

Distribution of the resonance mass in the untagged Signal Region of the $ ce$ channel for the post-fit background, the observed data, and the expected signal with $m_{LQ} = 1$ TeV.

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Search for dijet resonances in events with an isolated charged lepton using $\sqrt{s} = 13$ TeV proton-proton collision data collected by the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
JHEP 06 (2020) 151, 2020.
Inspire Record 1782373 DOI 10.17182/hepdata.94787

A search for dijet resonances in events with at least one isolated charged lepton is performed using $139~{\text{fb}}^{-1}$ of $\sqrt{s}=13$ TeV proton-proton collision data recorded by the ATLAS detector at the LHC. The dijet invariant-mass ($m_{jj}$) distribution constructed from events with at least one isolated electron or muon is searched in the region $0.22 < m_{jj} < 6.3$ TeV for excesses above a smoothly falling background from Standard Model processes. Triggering based on the presence of a lepton in the event reduces limitations imposed by minimum transverse momentum thresholds for triggering on jets. This approach allows smaller dijet invariant masses to be probed than in inclusive dijet searches, targeting a variety of new-physics models, for example ones in which a new state is produced in association with a leptonically decaying $W$ or $Z$ boson. No statistically significant deviation from the Standard Model background hypothesis is found. Limits on contributions from generic Gaussian signals with widths ranging from that determined by the detector resolution up to 15% of the resonance mass are obtained for dijet invariant masses ranging from 0.25 TeV to 6 TeV. Limits are set also in the context of several scenarios beyond the Standard Model, such as the Sequential Standard Model, a technicolor model, a charged Higgs boson model and a simplified Dark Matter model.

12 data tables match query

Observed and expected 95% credibility-level upper limits on the cross-section times acceptance times branching ratio for the techicolor model with production of $\rho_T$ decaying to $\pi_T W^{\pm}$. The table also shows the corresponding $1\sigma$ and $2\sigma$ bands for the expected limits. The limits are calculated using jets in events with at least one isolated lepton ($e$ or $\mu$) with $p_\text{T}^\ell \ge 60$ GeV.

Observed and expected 95% credibility-level upper limits on the cross-section times acceptance times branching ratio for $W' \to Z' W^{\pm}$ production in the Sequential Standard Model. The table also shows the corresponding $1\sigma$ and $2\sigma$ bands for the expected limits. The limits are calculated using jets in events with at least one isolated lepton ($e$ or $\mu$) with $p_\text{T}^\ell \ge 60$ GeV.

Observed and expected 95% credibility-level upper limits on the cross-section times branching ratio for the $tbH^+$ model. The table also shows the corresponding $1\sigma$ and $2\sigma$ bands for the expected limits. The limits are calculated using jets in events with at least one isolated lepton ($e$ or $\mu$) with $p_\text{T}^\ell \ge 60$ GeV.

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Performance of the missing transverse momentum triggers for the ATLAS detector during Run-2 data taking

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
JHEP 08 (2020) 080, 2020.
Inspire Record 1796953 DOI 10.17182/hepdata.95967

The factor of four increase in the LHC luminosity, from $0.5\times 10^{34}\,\textrm{cm}^{-2}\textrm{s}^{-1}$ to $2.0\times 10^{34}\textrm{cm}^{-2}\textrm{s}^{-1}$, and the corresponding increase in pile-up collisions during the 2015-2018 data-taking period, presented a challenge for ATLAS to trigger on missing transverse momentum. The output data rate at fixed threshold typically increases exponentially with the number of pile-up collisions, so the legacy algorithms from previous LHC data-taking periods had to be tuned and new approaches developed to maintain the high trigger efficiency achieved in earlier operations. A study of the trigger performance and comparisons with simulations show that these changes resulted in event selection efficiencies of >98% for this period, meeting and in some cases exceeding the performance of similar triggers in earlier run periods, while at the same time keeping the necessary bandwidth within acceptable limits.

67 data tables match query

A comparison of the measured cell $E_T^{miss}$ distribution with that predicted by the two-component model for two pile-up scenarios. The magenta points extend the measured distribution using L1 $E_T^{miss} > 30\,$GeV and L1 $E_T^{miss} > 50\,$GeV data. The red curve is the prediction from the calorimeter-resolution part of the model. The green curve is the high $E_T^{miss}$ tail's probability distribution for the mean number of $pp$ interactions $\mu$ in each figure. The blue curve is the full model prediction computed by combining the $E_T^{miss}$ from these two individual sources shown in red and green, each calculated for $\mu=\langle\mu\rangle$. The black points show the unbiased $E_T^{miss}$ distribution measured in data. Corresponds to a prediction for $\langle\mu\rangle = 25$.

A comparison of the measured cell $E_T^{miss}$ distribution with that predicted by the two-component model for two pile-up scenarios. The magenta points extend the measured distribution using L1 $E_T^{miss} > 30\,$GeV and L1 $E_T^{miss} > 50\,$GeV data. The red curve is the prediction from the calorimeter-resolution part of the model. The green curve is the high $E_T^{miss}$ tail's probability distribution for the mean number of $pp$ interactions $\mu$ in each figure. The blue curve is the full model prediction computed by combining the $E_T^{miss}$ from these two individual sources shown in red and green, each calculated for $\mu=\langle\mu\rangle$. The black points show the unbiased $E_T^{miss}$ distribution measured in data. Corresponds to a prediction for $\langle\mu\rangle = 25$.

A comparison of the measured cell $E_T^{miss}$ distribution with that predicted by the two-component model for two pile-up scenarios. The magenta points extend the measured distribution using L1 $E_T^{miss} > 30\,$GeV and L1 $E_T^{miss} > 50\,$GeV data. The red curve is the prediction from the calorimeter-resolution part of the model. The green curve is the high $E_T^{miss}$ tail's probability distribution for the mean number of $pp$ interactions $\mu$ in each figure. The blue curve is the full model prediction computed by combining the $E_T^{miss}$ from these two individual sources shown in red and green, each calculated for $\mu=\langle\mu\rangle$. The black points show the unbiased $E_T^{miss}$ distribution measured in data. Corresponds to a prediction for $\langle\mu\rangle = 25$.

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Version 2
Search for direct stau production in events with two hadronic $\tau$-leptons in $\sqrt{s} = 13$ TeV $pp$ collisions with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
Phys.Rev.D 101 (2020) 032009, 2020.
Inspire Record 1765529 DOI 10.17182/hepdata.92006

A search for the direct production of the supersymmetric partners of $\tau$-leptons (staus) in final states with two hadronically decaying $\tau$-leptons is presented. The analysis uses a dataset of $pp$ collisions corresponding to an integrated luminosity of $139$ fb$^{-1}$, recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected Standard Model background is observed. Limits are derived in scenarios of direct production of stau pairs with each stau decaying into the stable lightest neutralino and one $\tau$-lepton in simplified models where the two stau mass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidence level for a massless lightest neutralino.

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The observed upper limits on the model cross-section in units of pb for simplified models with combined ${\tilde{\tau}}^{+}_{R,L} {\tilde{\tau}}^{-}_{R,L}$ production. Three points at ${M({\tilde{\chi}}^{0}_{1})}=200GeV$ were removed from the plot but kept in the table because they overlapped with the plot's legend and are far from the exclusion contour.

The observed upper limits on the model cross-section in units of pb for simplified models with combined ${\tilde{\tau}}^{+}_{R,L} {\tilde{\tau}}^{-}_{R,L}$ production. Three points at ${M({\tilde{\chi}}^{0}_{1})}=200GeV$ were removed from the plot but kept in the table because they overlapped with the plot's legend and are far from the exclusion contour.

The observed upper limits on the model cross-section in units of pb for simplified models with ${\tilde{\tau}}_L {\tilde{\tau}}_L$ only production. Three points at $M({\tilde{\chi}}^{0}_{1})=200GeV$ were removed from the plot but kept in the table because they overlapped with the plot's legend and are far from the exclusion contour.

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Searches for lepton-flavour-violating decays of the Higgs boson in $\sqrt{s}=13$ TeV pp collisions with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
Phys.Lett.B 800 (2020) 135069, 2020.
Inspire Record 1743838 DOI 10.17182/hepdata.96299

This Letter presents direct searches for lepton flavour violation in Higgs boson decays, $H\rightarrow e\tau$ and $H\rightarrow\mu\tau$, performed with the ATLAS detector at the LHC. The searches are based on a data sample of proton-proton collisions at a centre-of-mass energy $\sqrt{s} = 13$ TeV, corresponding to an integrated luminosity of $36.1\,\mathrm{fb}^{-1}$. No significant excess is observed above the expected background from Standard Model processes. The observed (median expected) 95 % confidence-level upper limits on the lepton-flavour-violating branching ratios are $0.47\%$ ($0.34^{+0.13}_{-0.10}\,\%$) and $0.28\%$ ($0.37^{+0.14}_{-0.10}\,\%$) for $H\to e\tau$ and $H\to\mu\tau$, respectively.

2 data tables match query

95% CL upper limits on the branching ratio H --> e tau.

95% CL upper limits on the branching ratio H --> mu tau.


Search for a heavy Higgs boson decaying into a $Z$ boson and another heavy Higgs boson in the $\ell\ell bb$ and $\ell\ell WW$ final states in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
Eur.Phys.J.C 81 (2021) 396, 2021.
Inspire Record 1829873 DOI 10.17182/hepdata.95826

A search for a heavy neutral Higgs boson, $A$, decaying into a $Z$ boson and another heavy Higgs boson, $H$, is performed using a data sample corresponding to an integrated luminosity of 139 fb$^{-1}$ from proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded by the ATLAS detector at the LHC. The search considers the $Z$ boson decaying into electrons or muons and the $H$ boson into a pair of $b$-quarks or $W$ bosons. The mass range considered is 230-800 GeV for the $A$ boson and 130-700 GeV for the $H$ boson. The data are in good agreement with the background predicted by the Standard Model, and therefore 95% confidence-level upper limits for $\sigma \times B(A\rightarrow ZH) \times B(H\rightarrow bb$ or $H\rightarrow WW)$ are set. The upper limits are in the range 0.0062-0.380 pb for the $H\rightarrow bb$ channel and in the range 0.023-8.9 pb for the $H\rightarrow WW$ channel. An interpretation of the results in the context of two-Higgs-Doublet models is also given.

197 data tables match query

The mass distribution of the bb system before any mbb window cuts for the 2 tag category in b-associated production. The signal distribution for (mA, mH) = (600, 300) GeV is also shown, and is normalised such that the production cross-section times the branching ratios B(A->ZH)xB(H->bb) corresponds to 1 pb. Background components are displayed separately.

The mass distribution of the bb system before any mbb window cuts for the 3 tag category in b-associated production. The signal distribution for (mA, mH) = (600, 300) GeV is also shown, and is normalised such that the production cross-section times the branching ratios B(A->ZH)xB(H->bb) corresponds to 1 pb. Background components are displayed separately.

The mllbb mass distribution for the mbb window defined for (mA, mH)=(600, 300) GeV in the 2 tag category with gluon-gluon fusion production is shown. The number of entries shown in each bin is the number of events in that bin divided by the width of the bin. The signal distribution for (mA, mH) = (600, 300) GeV is also shown, and is normalised such that the production cross-section times the branching ratios B(A->ZH)xB(H->bb) corresponds to 1 pb. Background components are displayed separately.

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