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.


Studies of new Higgs boson interactions through nonresonant $HH$ production in the $b\bar{b}\gamma\gamma$ 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.
JHEP 01 (2024) 066, 2024.
Inspire Record 2712676 DOI 10.17182/hepdata.144918

A search for nonresonant Higgs boson pair production in the $b\bar{b}\gamma\gamma$ final state is performed using 140 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. This analysis supersedes and expands upon the previous nonresonant ATLAS results in this final state based on the same data sample. The analysis strategy is optimised to probe anomalous values not only of the Higgs ($H$) boson self-coupling modifier $\kappa_\lambda$ but also of the quartic $HHVV$ ($V=W,Z$) coupling modifier $\kappa_{2V}$. No significant excess above the expected background from Standard Model processes is observed. An observed upper limit $\mu_{HH}<4.0$ is set at 95% confidence level on the Higgs boson pair production cross-section normalised to its Standard Model prediction. The 95% confidence intervals for the coupling modifiers are $-1.4<\kappa_\lambda<6.9$ and $-0.5<\kappa_{2V}<2.7$, assuming all other Higgs boson couplings except the one under study are fixed to the Standard Model predictions. The results are interpreted in the Standard Model effective field theory and Higgs effective field theory frameworks in terms of constraints on the couplings of anomalous Higgs boson (self-)interactions.

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Observed (solid line) value of $-2\ln\Lambda$ as a function of $\kappa_{\lambda}$, when all other coupling modifiers are fixed to their SM predictions.

Expected (dashed line) value of $-2\ln\Lambda$ as a function of $\kappa_{\lambda}$, when all other coupling modifiers are fixed to their SM predictions.

Observed (solid line) value of $-2\ln\Lambda$ as a function of $\kappa_{2V}$, when all other coupling modifiers are fixed to their SM predictions.

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Search for a new $Z'$ gauge boson via the $pp \rightarrow W^{\pm(*)} \rightarrow Z' \mu^{\pm} \nu \rightarrow \mu^{\pm}\mu^{\mp}\mu^{\pm}\nu$ process 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-2024-042, 2024.
Inspire Record 2761384 DOI 10.17182/hepdata.149991

A search for a new $Z'$ gauge boson predicted by $L_{\mu}-L_{\tau}$ models, based on charged-current Drell-Yan production, $pp \rightarrow W^{\pm(*)} \rightarrow Z' \mu^{\pm} \nu \rightarrow \mu^{\pm}\mu^{\mp}\mu^{\pm}\nu$, is presented. The data sample used corresponds to an integrated luminosity of 140 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} = 13$ TeV recorded by the ATLAS detector at the Large Hadron Collider. The search examines a final state of $3\mu$ plus large missing transverse momentum. Upper limits are set on the $Z'$ production cross-section times branching ratio in the mass range of 5-81 GeV. After combining with the previous $Z'$ search using the neutral-current Drell-Yan production with a $4\mu$ final state, the most stringent exclusion limits to date are achieved in the parameter space of the $Z'$ coupling strength and mass.

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Observed and expected upper limits at 95% CL on the production cross-section times branching fraction of the process $pp\to W\to Z^{\prime}$ $\mu \nu \to \mu \mu \mu \nu$ as a function of $m_{Z^{\prime}}$.

Observed and expected upper limits at 95% CL on the coupling parameter $g_{Z^{\prime}}$ as a function of $m_{Z^{\prime}}$ from the statistical combination of the $3\mu$ and $4\mu$ channels.

Exclusion contour compared to the limits from the Neutrino Trident and the $B_{S}$ mixing experimental results.

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Search for pair production of squarks or gluinos decaying via sleptons or weak bosons in final states with two same-sign or three leptons with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 02 (2024) 107, 2024.
Inspire Record 2673888 DOI 10.17182/hepdata.139720

A search for pair production of squarks or gluinos decaying via sleptons or weak bosons is reported. The search targets a final state with exactly two leptons with same-sign electric charge or at least three leptons without any charge requirement. The analysed data set corresponds to an integrated luminosity of 139 fb$^{-1}$ of proton$-$proton collisions collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Multiple signal regions are defined, targeting several SUSY simplified models yielding the desired final states. A single control region is used to constrain the normalisation of the $WZ$+jets background. No significant excess of events over the Standard Model expectation is observed. The results are interpreted in the context of several supersymmetric models featuring R-parity conservation or R-parity violation, yielding exclusion limits surpassing those from previous searches. In models considering gluino (squark) pair production, gluino (squark) masses up to 2.2 (1.7) TeV are excluded at 95% confidence level.

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Observed exclusion limits at 95% CL from Fig 7(a) for $\tilde{g}$ decays into SM gauge bosons and $\tilde{\chi}^{0}_{1}$

Positive one $\sigma$ observed exclusion limits at 95% CL from Fig 7(a) for $\tilde{g}$ decays into SM gauge bosons and $\tilde{\chi}^{0}_{1}$

Negative one $\sigma$ observed exclusion limits at 95% CL from Fig 7(a) for $\tilde{g}$ decays into SM gauge bosons and $\tilde{\chi}^{0}_{1}$

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A statistical combination of ATLAS Run 2 searches for charginos and neutralinos at the LHC

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
CERN-EP-2024-018, 2024.
Inspire Record 2758009 DOI 10.17182/hepdata.149530

Statistical combinations of searches for charginos and neutralinos using various decay channels are performed using $139\,$fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=13\,$TeV with the ATLAS detector at the Large Hadron Collider. Searches targeting pure-wino chargino pair production, pure-wino chargino-neutralino production, or higgsino production decaying via Standard Model $W$, $Z$, or $h$ bosons are combined to extend the mass reach to the produced SUSY particles by 30-100 GeV. The depth of the sensitivity of the original searches is also improved by the combinations, lowering the 95% CL cross-section upper limits by 15%-40%.

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Expected 95% CL exclusion limits on the simplified models of chargino-pair production decaying via W bosons.

$+1\sigma$ expected 95% CL exclusion limits on the simplified models of chargino-pair production decaying via W bosons.

$-1\sigma$ expected 95% CL exclusion limits on the simplified models of chargino-pair production decaying via W bosons.

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Search for periodic signals in the dielectron and diphoton invariant mass spectra using 139 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} =$ 13 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 10 (2023) 079, 2023.
Inspire Record 2660845 DOI 10.17182/hepdata.140955

A search for physics beyond the Standard Model inducing periodic signals in the dielectron and diphoton invariant mass spectra is presented using 139 fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data collected by the ATLAS experiment at the LHC. Novel search techniques based on continuous wavelet transforms are used to infer the frequency of periodic signals from the invariant mass spectra and neural network classifiers are used to enhance the sensitivity to periodic resonances. In the absence of a signal, exclusion limits are placed at the 95% confidence level in the two-dimensional parameter space of the clockwork gravity model. Model-independent searches for deviations from the background-only hypothesis are also performed.

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The observed exclusion limit at 95% CL for the clockwork gravity model projected in the $k–M_{5}$ parameter space for the $ee$ channel for the case with mass thresholds.

The median expected exclusion limit at 95% CL for the clockwork gravity model projected in the $k–M_{5}$ parameter space for the $ee$ channel for the case with mass thresholds.

The expected plus one standard deviation exclusion limit at 95% CL for the clockwork gravity model projected in the $k–M_{5}$ parameter space for the $ee$ channel for the case with mass thresholds.

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Differential cross-section measurements of the production of four charged leptons in association with two jets using the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 01 (2024) 004, 2024.
Inspire Record 2690799 DOI 10.17182/hepdata.144086

Differential cross-sections are measured for the production of four charged leptons in association with two jets. These measurements are sensitive to final states in which the jets are produced via the strong interaction as well as to the purely-electroweak vector boson scattering process. The analysis is performed using proton-proton collision data collected by ATLAS at $\sqrt{s}=13$ TeV and with an integrated luminosity of 140 fb$^{-1}$. The data are corrected for the effects of detector inefficiency and resolution and are compared to state-of-the-art Monte Carlo event generator predictions. The differential cross-sections are used to search for anomalous weak-boson self-interactions that are induced by dimension-six and dimension-eight operators in Standard Model effective field theory.

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Predicted and observed yields as a function of $m_{jj}$ in the VBS-Enhanced region. Overflow events are included in the last bin of the distribution.

Predicted and observed yields as a function of $m_{jj}$ in the VBS-Suppressed region. Overflow events are included in the last bin of the distribution.

Predicted and observed yields as a function of $m_{4\ell}$ in the VBS-Enhanced region. Overflow events are included in the last bin of the distribution.

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Search for Resonant Production of Dark Quarks in the Dijet Final State with the ATLAS Detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 02 (2024) 128, 2024.
Inspire Record 2719976 DOI 10.17182/hepdata.145191

This paper presents a search for a new $Z^\prime$ resonance decaying into a pair of dark quarks which hadronise into dark hadrons before promptly decaying back as Standard Model particles. This analysis is based on proton-proton collision data recorded at $\sqrt{s}=13$ TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb$^{-1}$. After selecting events containing large-radius jets with high track multiplicity, the invariant mass distribution of the two highest-transverse-momentum jets is scanned to look for an excess above a data-driven estimate of the Standard Model multijet background. No significant excess of events is observed and the results are thus used to set 95 % confidence-level upper limits on the production cross-section times branching ratio of the $Z^\prime$ to dark quarks as a function of the $Z^\prime$ mass for various dark-quark scenarios.

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Distribution of the di-jet invariant mass, $m_{\mathrm{JJ}}$ for the data, the simulated multi-jet background and of some representative signals (models A, B, C and D with $m_{Z'}=2.5$ TeV), shown after applying the preselections described in the text. The simulated background is normalised to the data and the signals are normalised to a production cross-section of 10 fb.

Distributions of the number of tracks associated to the leading jet, $n_{track,1}$, for the data, the simulated multi-jet background and of some representative signals (models A, B, C and D with $m_{Z^\prime}=2.5$ TeV), shown after applying the preselections described in the text. All distributions are normalised to unity. The uncertainty band around the background prediction corresponds to the modelling uncertainty described in Section 6.

Distributions of the number of tracks associated to the subleading jet, $n_{track,2}$, for the data, the simulated multi-jet background and of some representative signals (models A, B, C and D with $m_{Z^\prime}=2.5$ TeV), shown after applying the preselections described in the text. All distributions are normalised to unity. The uncertainty band around the background prediction corresponds to the modelling uncertainty described in Section 6.

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Study of $Z \to ll\gamma$ decays at $\sqrt s~$= 8 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Dale ; et al.
Eur.Phys.J.C 84 (2024) 195, 2024.
Inspire Record 2712353 DOI 10.17182/hepdata.131524

This paper presents a study of $Z \to ll\gamma~$decays with the ATLAS detector at the Large Hadron Collider. The analysis uses a proton-proton data sample corresponding to an integrated luminosity of 20.2 fb$^{-1}$ collected at a centre-of-mass energy $\sqrt{s}$ = 8 TeV. Integrated fiducial cross-sections together with normalised differential fiducial cross-sections, sensitive to the kinematics of final-state QED radiation, are obtained. The results are found to be in agreement with state-of-the-art predictions for final-state QED radiation. First measurements of $Z \to ll\gamma\gamma$ decays are also reported.

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Unfolded $M(l^{+}\gamma)$ distribution for $Z \to ee\gamma$ process with dressed leptons and bkg subtraction. $M_{ll}>20$ GeV. Nexp.un f. = 63717.4 $\pm$ 252.4, NPowHeg truth =338714.

Unfolded $M(l^{-}\gamma)$ distribution for $Z \to ee\gamma$ process with dressed leptons and bkg subtraction. $M_{ll}>20$ GeV. Nexp.un f. = 63855.8 $\pm$ 252.7 , NPowHeg truth =338708.

Unfolded $M(l^{+}\gamma)$ distribution for $Z \to \mu\mu\gamma$ process with dressed leptons and bkg subtraction. $M_{ll}>20$ GeV. Nexp.un f. = 64809.8 $\pm$ 254.6, NPowHeg truth =634285.

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A precise measurement of the Z-boson double-differential transverse momentum and rapidity distributions in the full phase space of the decay leptons with the ATLAS experiment at $\sqrt s$ = 8 TeV

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
Eur.Phys.J.C 84 (2024) 315, 2024.
Inspire Record 2698794 DOI 10.17182/hepdata.144246

This paper presents for the first time a precise measurement of the production properties of the Z boson in the full phase space of the decay leptons. The measurement is obtained from proton-proton collision data collected by the ATLAS experiment in 2012 at $\sqrt s$ = 8 TeV at the LHC and corresponding to an integrated luminosity of 20.2 fb$^{-1}$. The results, based on a total of 15.3 million Z-boson decays to electron and muon pairs, extend and improve a previous measurement of the full set of angular coefficients describing Z-boson decay. The double-differential cross-section distributions in Z-boson transverse momentum p$_T$ and rapidity y are measured in the pole region, defined as 80 $<$ m $<$ 100 GeV, over the range $|y| <$ 3.6. The total uncertainty of the normalised cross-section measurements in the peak region of the p$_T$ distribution is dominated by statistical uncertainties over the full range and increases as a function of rapidity from 0.5-1.0% for $|y| <$ 2.0 to 2-7% at higher rapidities. The results for the rapidity-dependent transverse momentum distributions are compared to state-of-the-art QCD predictions, which combine in the best cases approximate N$^4$LL resummation with N$^3$LO fixed-order perturbative calculations. The differential rapidity distributions integrated over p$_T$ are even more precise, with accuracies from 0.2-0.3% for $|y| <$ 2.0 to 0.4-0.9% at higher rapidities, and are compared to fixed-order QCD predictions using the most recent parton distribution functions. The agreement between data and predictions is quite good in most cases.

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Measured $p_T$ cross sections in full-lepton phase space for |y| < 0.4.

Measured $p_T$ cross sections in full-lepton phase space for 0.4 < |y| < 0.8.

Measured $p_T$ cross sections in full-lepton phase space for 0.8 < |y| < 1.2.

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