| 131. |
- Aad, G., et al.
(författare)
-
Search for pair-produced vector-like top and bottom partners in events with large missing transverse momentum in pp collisions with the ATLAS detector
- 2023
-
Ingår i: European Physical Journal C. - : Institute for Ionics. - 1434-6044 .- 1434-6052. ; 83:8
-
Tidskriftsartikel (refereegranskat)abstract
- A search for pair-produced vector-like quarks using events with exactly one lepton (e or μ), at least four jets including at least one b-tagged jet, and large missing transverse momentum is presented. Data from proton–proton collisions at a centre-of-mass energy of √s=13 TeV, recorded by the ATLAS detector at the LHC from 2015 to 2018 and corresponding to an integrated luminosity of 139 fb−1, are analysed. Vector-like partners T and B of the top and bottom quarks are considered, as is a vector-like X with charge +5/3, assuming their decay into a W, Z, or Higgs boson and a third-generation quark. No significant deviations from the Standard Model expectation are observed. Upper limits on the production cross-section of T and B quark pairs as a function of their mass are derived for various decay branching ratio scenarios. The strongest lower limits on the masses are 1.59 TeV assuming mass-degenerate vector-like quarks and branching ratios corresponding to the weak-isospin doublet model, and 1.47 TeV (1.46 TeV) for exclusive T→Zt (B/X→Wt) decays. In addition, lower limits on the T and B quark masses are derived for all possible branching ratios.
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| 132. |
- Aad, G, et al.
(författare)
-
Search for pair production of higgsinos in events with two Higgs bosons and missing transverse momentum in Formula Presented Formula Presented collisions at the ATLAS experiment
- 2024
-
Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 109:11
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a search for pair production of higgsinos, the supersymmetric partners of the Higgs bosons, in scenarios with gauge-mediated supersymmetry breaking. Each higgsino is assumed to decay into a Higgs boson and a nearly massless gravitino. The search targets events where each Higgs boson decays into Formula Presented, leading to a reconstructed final state with at least three energetic Formula Presented-jets and missing transverse momentum. Two complementary analysis channels are used, with each channel specifically targeting either low or high values of the higgsino mass. The low-mass (high-mass) channel exploits Formula Presented of Formula Presented data collected by the ATLAS detector during Run 2 of the Large Hadron Collider. No significant excess above the Standard Model prediction is found. At 95% confidence level, masses between 130 GeV and 940 GeV are excluded for higgsinos decaying exclusively into Higgs bosons and gravitinos. Exclusion limits as a function of the higgsino decay branching ratio to a Higgs boson are also reported. © 2024 CERN, for the ATLAS Collaboration.
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| 133. |
- Aad, G, et al.
(författare)
-
Search for pair production of scalar leptoquarks decaying into first- or second-generation leptons and top quarks in proton–proton collisions at √s = 13 TeV with the ATLAS detector
- 2021
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:4
-
Tidskriftsartikel (refereegranskat)abstract
- A search for pair production of scalar leptoquarks, each decaying into either an electron or a muon and a top quark, is presented. This is the first leptoquark search using ATLAS data to investigate top-philic cross-generational couplings that could provide explanations for recently observed anomalies in B meson decays. This analysis targets high leptoquark masses which cause the decay products of each resultant top quark to be contained within a single high-pT large-radius jet. The full Run 2 dataset is exploited, consisting of 139fb-1 of data collected from proton–proton collisions at s=13TeV from 2015 to 2018 with the ATLAS detector at the CERN Large Hadron Collider. In the absence of any significant deviation from the background expectation, lower limits on the leptoquark masses are set at 1480GeV and 1470GeV for the electron and muon channel, respectively. © 2021, The Author(s).
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| 134. |
- Aad, G., et al.
(författare)
-
Search for pair-production of vector-like quarks in lepton+jets final states containing at least one b-tagged jet using the Run 2 data from the ATLAS experiment
- 2024
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 854
-
Tidskriftsartikel (refereegranskat)abstract
- A search is presented for the pair-production of heavy vector-like quarks in the lepton+jets final state using 140 fb−1 of proton–proton collisions at s=13 TeV collected with the ATLAS detector. The search is optimised for vector-like top-quarks (T) that decay into a W boson and a b-quark, with one W boson decaying leptonically and the other hadronically. Other vector-like quark flavours and decay modes are also considered. Events are selected with one high transverse-momentum electron or muon, large missing transverse momentum, a large-radius jet identified as a W boson, and multiple small-radius jets, at least one of which is b-tagged. Vector-like T-quarks with 100% branching ratio to Wb are excluded at 95% CL for masses below 1700 GeV. These limits are also applied to vector-like Y-quarks, which decay exclusively into a W boson and a b-quark. Isospin singlets with B(T→Wb:Ht:Zt)=1/2:1/4:1/4 are excluded for masses below 1360 GeV. © 2024 The Author(s)
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| 135. |
- Aad, G., et al.
(författare)
-
Search for pairs of muons with small displacements in pp collisions at √s=13 TeV with the ATLAS detector
- 2023
-
Ingår i: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 846
-
Tidskriftsartikel (refereegranskat)abstract
- A search for new phenomena giving rise to pairs of opposite electrically charged muons with impact parameters in the millimeter range is presented, using 139 fb−1 of √s=13 TeV pp collision data from the ATLAS detector at the LHC. The search targets the gap in coverage between existing searches targeting final states with leptons with large displacement and prompt leptons. No significant excess over the background expectation is observed and exclusion limits are set on the mass of long-lived scalar supersymmetric muon-partners (smuons) with much lower lifetimes than previously targeted by displaced muon searches. Smuon lifetimes down to 1 ps are excluded for a smuon mass of 100 GeV, and smuon masses up to 520 GeV are excluded for a proper lifetime of 10 ps, at 95% confidence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields.
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| 136. |
- Aad, G, et al.
(författare)
-
Search for pairs of scalar leptoquarks decaying into quarks and electrons or muons in √s = 13 TeV pp collisions with the ATLAS detector
- 2020
-
Ingår i: Journal of High Energy Physics. - : Springer Nature. - 1029-8479 .- 1126-6708. ; 2020:10
-
Tidskriftsartikel (refereegranskat)abstract
- 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 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. [Figure not available: see fulltext.] © 2020, The Author(s).
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| 137. |
- Aad, G, et al.
(författare)
-
Search for phenomena beyond the Standard Model in events with large b-jet multiplicity using the ATLAS detector at the LHC
- 2021
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:1
-
Tidskriftsartikel (refereegranskat)abstract
- A search is presented for new phenomena in events characterised by high jet multiplicity, no leptons (electrons or muons), and four or more jets originating from the fragmentation of b-quarks (b-jets). The search uses 139fb-1 of s = 13 TeV proton–proton collision data collected by the ATLAS experiment at the Large Hadron Collider during Run 2. The dominant Standard Model background originates from multijet production and is estimated using a data-driven technique based on an extrapolation from events with low b-jet multiplicity to the high b-jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits that constrain simplified models of R-parity-violating supersymmetry are determined. The exclusion limits reach 950 GeV in top-squark mass in the models considered. © 2021, The Author(s).
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| 138. |
- Aad, G, et al.
(författare)
-
Search for resonances decaying into a weak vector boson and a Higgs boson in the fully hadronic final state produced in proton-proton collisions at s =13 TeV with the ATLAS detector
- 2020
-
Ingår i: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 102:11
-
Tidskriftsartikel (refereegranskat)abstract
- A search for heavy resonances decaying into a W or Z boson and a Higgs boson produced in proton-proton collisions at the Large Hadron Collider at s=13 TeV is presented. The analysis utilizes the dominant W→qq¯′ or Z→qq¯ and H→bb¯ decays with substructure techniques applied to large-radius jets. A sample corresponding to an integrated luminosity of 139 fb-1 collected with the ATLAS detector is analyzed and no significant excess of data is observed over the background prediction. The results are interpreted in the context of the heavy vector triplet model with spin-1 W′ and Z′ bosons. Upper limits on the cross section are set for resonances with mass between 1.5 and 5.0 TeV, ranging from 6.8 to 0.53 fb for W′→WH and from 8.7 to 0.53 fb for Z′→ZH at the 95% confidence level. © 2020 CERN.
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| 139. |
- Aad, G, et al.
(författare)
-
Search for singly produced vectorlike top partners in multilepton final states with Formula Presented of Formula Presented collision data at Formula Presented with the ATLAS detector
- 2024
-
Ingår i: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 109:11
-
Tidskriftsartikel (refereegranskat)abstract
- A search for the single production of a vectorlike top partner (Formula Presented) with mass greater than 1 TeV decaying into a Formula Presented boson and a top quark is presented, using the full Run 2 dataset corresponding to Formula Presented of Formula Presented collisions at Formula Presented, collected in 2015-2018 with the ATLAS detector at the Large Hadron Collider. The targeted final state is characterized by the presence of a pair of electrons or muons with opposite-sign charges which form a Formula Presented-boson candidate, as well as by the presence of Formula Presented-tagged jets and forward jets. Events with exactly two or at least three leptons are categorized into two independently optimized analysis channels. No significant excess above the background expectation is observed and the results from the two channels are statistically combined to set exclusion limits at 95% confidence level on the masses and couplings of Formula Presented. The results are interpreted in several benchmark scenarios to set limits on the mass and universal coupling strength (Formula Presented) of the vectorlike quark. For singlet Formula Presented quarks, Formula Presented values between 0.22 and 0.64 are excluded for masses between 1000 and 1975 GeV. For Formula Presented quarks in the doublet scenario, where the production cross section is much lower, Formula Presented values between 0.54 and 0.88 are excluded for masses between 1000 and 1425 GeV. © 2024 CERN, for the ATLAS Collaboration.
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| 140. |
- Aad, G, et al.
(författare)
-
Search for squarks and gluinos in final states with one isolated lepton, jets, and missing transverse momentum at √s=13 with the ATLAS detector
- 2021
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:7
-
Tidskriftsartikel (refereegranskat)abstract
- The results of a search for gluino and squark pair production with the pairs decaying via the lightest charginos into a final state consisting of two W bosons, the lightest neutralinos (χ~10), and quarks, are presented: the signal is characterised by the presence of a single charged lepton (e± or μ±) from a W boson decay, jets, and missing transverse momentum. The analysis is performed using 139 fb- 1 of proton–proton collision data taken at a centre-of-mass energy s=13 delivered by the Large Hadron Collider and recorded by the ATLAS experiment. No statistically significant excess of events above the Standard Model expectation is found. Limits are set on the direct production of squarks and gluinos in simplified models. Masses of gluino (squark) up to 2.2 (1.4) are excluded at 95% confidence level for a light χ~10.
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