Search for vector-boson resonances decaying into a top quark and a bottom quark using $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 12 (2023) 073, 2023.
Inspire Record 2688749 DOI 10.17182/hepdata.142662

A search for a new massive charged gauge boson, $W'$, is performed with the ATLAS detector at the LHC. The dataset used in this analysis was collected from proton-proton collisions at a centre-of-mass energy of $\sqrt{s} =13$ TeV, and corresponds to an integrated luminosity of 139 fb$^{-1}$. The reconstructed $tb$ invariant mass is used to search for a $W'$ boson decaying into a top quark and a bottom quark. The result is interpreted in terms of a $W'$ boson with purely right-handed or left-handed chirality in a mass range of 0.5-6 TeV. Different values for the coupling of the $W'$ boson to the top and bottom quarks are considered, taking into account interference with single-top-quark production in the $s$-channel. No significant deviation from the background prediction is observed. The results are expressed as upper limits on the $W' \rightarrow tb$ production cross-section times branching ratio as a function of the $W'$-boson mass and in the plane of the coupling vs the $W'$-boson mass.

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<b>- - - - - - - - Overview of HEPData Record - - - - - - - -</b> <br><br> <b>Exclusion contours:</b> <ul> <li><a href="?table=contour_lh">$W^{\prime}_L$ exclusion contour</a> <li><a href="?table=contour_rh">$W^{\prime}_R$ exclusion contour</a> </ul> <b>Upper limits:</b> <ul> <li><a href="?table=limit_lh_gf05">$W^{\prime}_L$ $g^{\prime}/g$ = 0.5 upper limit</a> <li><a href="?table=limit_lh_gf10">$W^{\prime}_L$ $g^{\prime}/g$ = 1.0 upper limit</a> <li><a href="?table=limit_lh_gf20">$W^{\prime}_L$ $g^{\prime}/g$ = 2.0 upper limit</a> <li><a href="?table=limit_rh_gf05">$W^{\prime}_R$ $g^{\prime}/g$ = 0.5 upper limit</a> <li><a href="?table=limit_rh_gf10">$W^{\prime}_R$ $g^{\prime}/g$ = 1.0 upper limit</a> <li><a href="?table=limit_rh_gf20">$W^{\prime}_R$ $g^{\prime}/g$ = 2.0 upper limit</a> </ul> <b>Kinematic distributions:</b> <ul> <li><a href="?table=0l_sr1">0L channel Signal Region 1</a> <li><a href="?table=0l_sr2">0L channel Signal Region 2</a> <li><a href="?table=0l_sr3">0L channel Signal Region 3</a> <li><a href="?table=0l_vr">0L channel Validation Region</a> <li><a href="?table=1l_sr_2j1b">1L channel 2j1b Signal Region</a> <li><a href="?table=1l_sr_3j1b">1L channel 3j1b Signal Region</a> <li><a href="?table=1l_sr_2j2b">1L channel 2j2b Signal Region</a> <li><a href="?table=1l_sr_3j2b">1L channel 3j2b Signal Region</a> <li><a href="?table=1l_cr_2j1b">1L channel 2j1b Control Region</a> <li><a href="?table=1l_cr_3j1b">1L channel 3j1b Control Region</a> <li><a href="?table=1l_vr_2j1b">1L channel 2j1b Validation Region</a> <li><a href="?table=1l_vr_3j1b">1L channel 3j1b Validation Region</a> </ul> <b>Acceptance and efficiencies:</b> <ul> <li><a href="?table=acc_0l_lh_gf10">0L channel $W^{\prime}_L$ $g^{\prime}/g$ = 1.0 Acc. X Eff.</a> <li><a href="?table=acc_0l_lh_gf05">0L channel $W^{\prime}_L$ $g^{\prime}/g$ = 0.5 Acc. X Eff.</a> <li><a href="?table=acc_0l_lh_gf20">0L channel $W^{\prime}_L$ $g^{\prime}/g$ = 2.0 Acc. X Eff.</a> <li><a href="?table=acc_1l_lh_gf10">1L channel $W^{\prime}_L$ $g^{\prime}/g$ = 1.0 Acc. X Eff.</a> <li><a href="?table=acc_1l_lh_gf05">1L channel $W^{\prime}_L$ $g^{\prime}/g$ = 0.5 Acc. X Eff.</a> <li><a href="?table=acc_1l_lh_gf20">1L channel $W^{\prime}_L$ $g^{\prime}/g$ = 2.0 Acc. X Eff.</a> <li><a href="?table=acc_0l_rh_gf10">0L channel $W^{\prime}_R$ $g^{\prime}/g$ = 1.0 Acc. X Eff.</a> <li><a href="?table=acc_0l_rh_gf05">0L channel $W^{\prime}_R$ $g^{\prime}/g$ = 0.5 Acc. X Eff.</a> <li><a href="?table=acc_0l_rh_gf20">0L channel $W^{\prime}_R$ $g^{\prime}/g$ = 2.0 Acc. X Eff.</a> <li><a href="?table=acc_1l_rh_gf10">1L channel $W^{\prime}_R$ $g^{\prime}/g$ = 1.0 Acc. X Eff.</a> <li><a href="?table=acc_1l_rh_gf05">1L channel $W^{\prime}_R$ $g^{\prime}/g$ = 0.5 Acc. X Eff.</a> <li><a href="?table=acc_1l_rh_gf20">1L channel $W^{\prime}_R$ $g^{\prime}/g$ = 2.0 Acc. X Eff.</a> </ul>

Distribution (events/100 GeV) of the reconstructed $m_{tb}$ for data and backgrounds in the 0-lepton channel's signal region 1 after the background-only fit to data. The systematics uncertainty is shown for the post-fit background sum, including the background statistical uncertainty. The individual background components are obtained after the fit, too. There are also the pre-fit background sum and the expected signal distribution. The distribution of the $W^{\prime}$ boson signal for a mass of 3 TeV is normalised to the predicted cross-section. The last bin in each distribution includes overflow.

Distribution (events/100 GeV) of the reconstructed $m_{tb}$ for data and backgrounds in the 0-lepton channel's signal region 2 after the background-only fit to data. The systematics uncertainty is shown for the post-fit background sum, including the background statistical uncertainty. The individual background components are obtained after the fit, too. There are also the pre-fit background sum and the expected signal distribution. The distribution of the $W^{\prime}$ boson signal for a mass of 3 TeV is normalised to the predicted cross-section. The last bin in each distribution includes overflow.

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Search for leptoquark pair production decaying into $te^- \bar{t}e^+$ or $t\mu^- \bar{t}\mu^+$ in multi-lepton final states in $pp$ collisions at 13 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Dale ; et al.
CERN-EP-2023-087, 2023.
Inspire Record 2673386 DOI 10.17182/hepdata.150507

A search for leptoquark pair production decaying into $te^- \bar{t}e^+$ or $t\mu^- \bar{t}\mu^+$ in final states with multiple leptons is presented. The search is based on a dataset of $pp$ collisions at $\sqrt{s}$=13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139~fb$^{-1}$. Events are selected with two or more light leptons (electron or muon) and at least two jets out of which at least one jet is identified as coming from a $b$-hadron. Four signal regions, with the requirement of at least three light leptons, are considered based on the number of leptons of a given flavour. The main background processes are estimated using dedicated control regions in a simultaneous fit with the signal regions to data. No excess above the Standard Model background prediction is observed and 95% confidence level limits on the production cross section times branching ratio are derived as a function of the leptoquark mass. Under the assumption of exclusive decays into $te^{-}$ ($t\mu^{-}$), the corresponding lower limit on the scalar mixed-generation leptoquark mass $m_{\mathrm{LQ}_{\mathrm{mix}}^{\mathrm{d}}}$ is at 1.58 (1.59) TeV and on the vector leptoquark mass $m_{\tilde{U}_1}$ at 1.67 (1.67) TeV in the minimal coupling scenario and at 1.95 (1.95) TeV in the Yang-Mills scenario.

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Selection efficiency times acceptance summed over two signal regions for the scalar leptoquark signals as a function of $m_{\mathrm{LQ}_{mix}^{\mathrm{d}}}$, assuming B = 1.

Selection efficiency times acceptance summed over two signal regions for the vector leptoquark signals as a function of $m_{\tilde{U}_{1}}$, assuming B = 1 and Yang-Mills coupling scenario.

Summary of the observed and expected 95% CL upper limits on the cross section for $\mathrm{LQ}_{\mathrm{mix}}^{\mathrm{d}}$ pair production as a function of $m_{\mathrm{LQ}_{\mathrm{mix}}^{\mathrm{d}}}$ under the assumptions of B(LQ$\rightarrow te$)=1.

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ATLAS Run 2 searches for electroweak production of supersymmetric particles interpreted within the pMSSM

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
CERN-EP-2024-021, 2024.
Inspire Record 2755168 DOI 10.17182/hepdata.149493

A summary of the constraints from searches performed by the ATLAS Collaboration for the electroweak production of charginos and neutralinos is presented. Results from eight separate ATLAS searches are considered, each using 140 fb$^{-1}$ of proton-proton data at a centre-of-mass energy of $\sqrt{s}$=13 TeV collected at the Large Hadron Collider during its second data-taking run. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, where R-parity conservation is assumed and the lightest supersymmetric particle is assumed to be the lightest neutralino. Constraints from previous electroweak, flavour and dark matter related measurements are also considered. The results are presented in terms of constraints on supersymmetric particle masses and are compared with limits from simplified models. Also shown is the impact of ATLAS searches on parameters such as the dark matter relic density and the spin-dependent and spin-independent scattering cross-sections targeted by direct dark matter detection experiments. The Higgs boson and Z boson `funnel regions', where a low-mass neutralino would not oversaturate the dark matter relic abundance, are almost completely excluded by the considered constraints. Example spectra for non-excluded supersymmetric models with light charginos and neutralinos are also presented.

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SLHA files and exclusion information (in CSV format) are available to download for the pMSSM models in this paper. Please refer to <a href="https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2020-15/inputs/ATLAS_EW_pMSSM_Run2.html">this web page</a> for download links along with a description of the contents.

SLHA files and exclusion information (in CSV format) are available to download for the pMSSM models in this paper. Please refer to <a href="https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2020-15/inputs/ATLAS_EW_pMSSM_Run2.html">this web page</a> for download links along with a description of the contents.


Measurement and interpretation of same-sign $W$ boson pair production in association with two jets 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 04 (2024) 026, 2024.
Inspire Record 2729396 DOI 10.17182/hepdata.141650

This paper presents the measurement of fiducial and differential cross sections for both the inclusive and electroweak production of a same-sign $W$-boson pair in association with two jets ($W^\pm W^\pm jj$) using 139 fb$^{-1}$ of proton-proton collision data recorded at a centre-of-mass energy of $\sqrt{s}=13$ TeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed by selecting two same-charge leptons, electron or muon, and at least two jets with large invariant mass and a large rapidity difference. The measured fiducial cross sections for electroweak and inclusive $W^\pm W^\pm jj$ production are $2.92 \pm 0.22\, \text{(stat.)} \pm 0.19\, \text{(syst.)}$ fb and $3.38 \pm 0.22\, \text{(stat.)} \pm 0.19\, \text{(syst.)}$ fb, respectively, in agreement with Standard Model predictions. The measurements are used to constrain anomalous quartic gauge couplings by extracting 95% confidence level intervals on dimension-8 operators. A search for doubly charged Higgs bosons $H^{\pm\pm}$ that are produced in vector-boson fusion processes and decay into a same-sign $W$ boson pair is performed. The largest deviation from the Standard Model occurs for an $H^{\pm\pm}$ mass near 450 GeV, with a global significance of 2.5 standard deviations.

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Fiducial differential cross section of the electroweak $W^\pm W^\pm jj$ production as a function of $m_{\ell\ell}$. The correlation of uncertainties of the measured cross section across bins is presented in Table 11.

Fiducial differential cross section of the electroweak $W^\pm W^\pm jj$ production as a function of $m_{\mathrm{T}}$. The correlation of uncertainties of the measured cross section across bins is presented in Table 12.

Fiducial differential cross section of the electroweak $W^\pm W^\pm jj$ production as a function of $m_{\mathrm{jj}}$. The correlation of uncertainties of the measured cross section across bins is presented in Table 13.

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Version 2
Search for nearly mass-degenerate higgsinos using low-momentum mildly-displaced tracks in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Aakvaag, Erlend ; Abbott, Braden Keim ; et al.
CERN-EP-2024-012, 2024.
Inspire Record 2751400 DOI 10.17182/hepdata.146944

Higgsinos with masses near the electroweak scale can solve the hierarchy problem and provide a dark matter candidate, while detecting them at the LHC remains challenging if their mass-splitting is $\mathcal{O}$(1 GeV). This Letter presents a novel search for nearly mass-degenerate higgsinos in events with an energetic jet, missing transverse momentum, and a low-momentum track with a significant transverse impact parameter using 140 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}$ = 13 TeV collected by the ATLAS experiment. For the first time since LEP, a range of mass-splittings between the lightest charged and neutral higgsinos from 0.3 GeV to 0.9 GeV is excluded at 95% confidence level, with a maximum reach of approximately 170 GeV in the higgsino mass.

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Number of expected and observed data events in the SR (top), and the model-independent upper limits obtained from their consistency (bottom). The symbol $\tau_{\ell}$ ($\tau_{h}$) refers to fully-leptonic (hadron-involved) tau decays. The Others category includes contributions from minor background processes including $t\bar{t}$, single-top and diboson. The individual uncertainties can be correlated and do not necessarily sum up in quadrature to the total uncertainty. The bottom section shows the observed 95% CL upper limits on the visible cross-section ($\langle\epsilon\sigma\rangle_{\mathrm{obs}}^{95}$), on the number of generic signal events ($S_{\mathrm{obs}}^{95}$) as well as the expected limit ($S_{\mathrm{exp}}^{95}$) given the expected number (and $\pm 1\sigma$ deviations from the expectation) of background events.

Expected (dashed black line) and observed (solid red line) 95% CL exclusion limits on the higgsino simplified model being considered. These are shown with $\pm 1\sigma_{\mathrm{exp}}$ (yellow band) from experimental systematic and statistical uncertainties, and with $\pm 1\sigma_{\mathrm{theory}}^{\mathrm{SUSY}}$ (red dotted lines) from signal cross-section uncertainties, respectively. The limits set by the latest ATLAS searches using the soft lepton and disappearing track signatures are illustrated by the blue and green regions, respectively, while the limit imposed by the LEP experiments is shown in gray. The dot-dashed gray line indicates the predicted mass-splitting for the pure higgsino scenario.

Expected (dashed black line) and observed (solid red line) 95% CL exclusion limits on the higgsino simplified model being considered. These are shown with $\pm 1\sigma_{\mathrm{exp}}$ (yellow band) from experimental systematic and statistical uncertainties, and with $\pm 1\sigma_{\mathrm{theory}}^{\mathrm{SUSY}}$ (red dotted lines) from signal cross-section uncertainties, respectively. The limits set by the latest ATLAS searches using the soft lepton and disappearing track signatures are illustrated by the blue and green regions, respectively, while the limit imposed by the LEP experiments is shown in gray. The dot-dashed gray line indicates the predicted mass-splitting for the pure higgsino scenario.

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Measurement of multi-particle azimuthal correlations in $pp$, $p$+Pb and low-multiplicity Pb+Pb collisions with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Eur.Phys.J.C 77 (2017) 428, 2017.
Inspire Record 1599077 DOI 10.17182/hepdata.77996

Multi-particle cumulants and corresponding Fourier harmonics are measured for azimuthal angle distributions of charged particles in $pp$ collisions at $\sqrt{s}$ = 5.02 and 13 TeV and in $p$+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, and compared to the results obtained for low-multiplicity Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. These measurements aim to assess the collective nature of particle production. The measurements of multi-particle cumulants confirm the evidence for collective phenomena in $p$+Pb and low-multiplicity Pb+Pb collisions. On the other hand, the $pp$ results for four-particle cumulants do not demonstrate collective behaviour, indicating that they may be biased by contributions from non-flow correlations. A comparison of multi-particle cumulants and derived Fourier harmonics across different collision systems is presented as a function of the charged-particle multiplicity. For a given multiplicity, the measured Fourier harmonics are largest in Pb+Pb, smaller in $p$+Pb and smallest in $pp$ collisions. The $pp$ results show no dependence on the collision energy, nor on the multiplicity.

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$c_2\{4\}$ cumulants for reference particles with 0.3 $< p_T <$ 3.0 GeV selected according to $M_{ref}$ (EvSel_$M_{ref}$) for pp collisions at $\sqrt{s}$= 5.02 TeV.

$c_2\{4\}$ cumulants for reference particles with 0.3 $< p_T <$ 3.0 GeV selected according to $M_{ref}$ (EvSel_$M_{ref}$) for pp collisions at $\sqrt{s}$= 13 TeV.

$c_2\{4\}$ cumulants for reference particles with 0.3 $< p_T <$ 3.0 GeV selected according to $M_{ref}$ (EvSel_$M_{ref}$) for pPb collisions at $\sqrt{ s_{NN} }$= 5.02 TeV.

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Measurement of the $t\bar{t}$ cross section and its ratio to the $Z$ production cross section using $pp$ collisions at $\sqrt{s} = 13.6$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
Phys.Lett.B 848 (2024) 138376, 2024.
Inspire Record 2689657 DOI 10.17182/hepdata.143515

The inclusive top-quark-pair production cross section $\sigma_{t\bar{t}}$ and its ratio to the $Z$-boson production cross section have been measured in proton--proton collisions at $\sqrt{s} = 13.6$ TeV, using 29 fb${}^{-1}$ of data collected in 2022 with the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge electron-muon pair and $b$-tagged jets, and assuming Standard Model decays, the top-quark-pair production cross section is measured to be $\sigma_{t\bar{t}} = 850 \pm 3\mathrm{(stat.)}\pm 18\mathrm{(syst.)}\pm 20\mathrm{(lumi.)}$ pb. The ratio of the $t\bar{t}$ and the $Z$-boson production cross sections is also measured, where the $Z$-boson contribution is determined for inclusive $e^+e^-$ and $\mu^+\mu^-$ events in a fiducial phase space. The relative uncertainty on the ratio is reduced compared to the $t\bar{t}$ cross section, thanks to the cancellation of several systematic uncertainties. The result for the ratio, $R_{t\bar{t}/Z} = 1.145 \pm 0.003\mathrm{(stat.)}\pm 0.021\mathrm{(syst.)}\pm 0.002\mathrm{(lumi.)}$ is consistent with the Standard Model prediction using the PDF4LHC21 PDF set.

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The fiducial phase-space definition for the $Z$-boson measurement. Born-level leptons are used.

The measured $t\bar{t}$ cross section and the ratio of the cross sections of $t\bar{t}$ and the $Z$-boson. Full phase-space is considered for $t\bar{t}$, while fiducial phase-space is considered for the $Z$-boson.

Table with pre-fit yields in the four regions used in the measurement

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Evidence for the Higgs boson decay to a $Z$ boson and a photon at the LHC

The ATLAS & CMS collaborations Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
Phys.Rev.Lett. 132 (2024) 021803, 2024.
Inspire Record 2666787 DOI 10.17182/hepdata.142406

The first evidence for the Higgs boson decay to a $Z$ boson and a photon is presented, with a statistical significance of 3.4 standard deviations. The result is derived from a combined analysis of the searches performed by the ATLAS and CMS Collaborations with proton-proton collision data sets collected at the CERN Large Hadron Collider (LHC) from 2015 to 2018. These correspond to integrated luminosities of around 140 fb$^{-1}$ for each experiment, at a center-of-mass energy of 13 TeV. The measured signal yield is $2.2\pm0.7$ times the Standard Model prediction, and agrees with the theoretical expectation within 1.9 standard deviations.

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The negative profile log-likelihood test statistic, where $\Lambda$ represents the likelihood ratio, as a function of the signal strength $\mu$ derived from the ATLAS data, the CMS data, and the combined result.