ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). Search for pair-production of vector-like quarks in lepton plus jets final states containing at least one b-tagged jet using the Run 2 data from the ATLAS experiment. Phys. Lett. B, 854, 138743–28pp.
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 root 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.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). Combination of searches for pair-produced leptoquarks at √s=13 TeV with the ATLAS detector. Phys. Lett. B, 854, 138736–24pp.
Abstract: A statistical combination of various searches for pair-produced leptoquarks is presented, using the full LHC Run 2 (2015-2018) data set of 139 fb(-1) collected with the ATLAS detector from proton-proton collisions at a centre-of-mass energy of root s = 13 TeV. All possible decays of the leptoquarks into quarks of the third generation and charged or neutral leptons of any generation are investigated. Since no significant deviations from the Standard Model expectation are observed in any of the individual analyses, combined exclusion limits are set on the production cross-sections for scalar and vector leptoquarks. The resulting lower bounds on leptoquark masses exceed those from the individual analyses by up to 100 GeV, depending on the signal hypothesis.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). Measurement of the Z boson invisible width at √s=13 TeV with the ATLAS detector. Phys. Lett. B, 854, 138705–25pp.
Abstract: A measurement of the invisible width of the boson using events with jets and missing transverse momentum is presented using 37 fb(-1) of 13 TeV proton-proton data collected by the ATLAS detector in 2015 and 2016. The ratio of Z -> inv to Z -> ll events, where inv refers to non-detected particles and l is either an electron or a muon, is measured and corrected for detector effects. Events with at least one energetic central jet with p(T) >= 110 GeV are selected for both the Z -> inv and Z -> ll final states to obtain a similar phase space in the ratio. The invisible width is measured to be 506 +/- 2 (stat.) +/- 12 (syst.) MeV and is the single most precise recoil-based measurement. The result is in agreement with the most precise determination from LEP and the Standard Model prediction based on three neutrino generations.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). Measurement of t-channel single-top-quark production in pp collisions at √s=5.02 TeV with the ATLAS detector. Phys. Lett. B, 854, 138726–22pp.
Abstract: The observation of the electroweak production of single-top-quarks is made using 255 pb(-1) of proton-proton collision data recorded at root s = 5.02 TeV with the ATLAS detector at the Large Hadron Collider. An event selection is used to identify single-top-quark candidates arising from..-channel production with the top quark decaying semi-leptonically. Events passing the selection are then used to measure the inclusive cross-section for the combined production of single-top-quarks and antiquarks, sigma(tq + (t) over barq), and the ratio R-t between these two. They are measured to be sigma(tq + (t) over barq) = 27.1(-4.1)(+4.4)(stat.)(-3.7)(+4.4)(syst.) pb and R-t = 2.73(-0.82)(+1.43)(stat.)(-0.29)(+1.01)(syst.). The individual single-top-quark (tq) and single-top-antiquark ((t) over barq) production cross-sections are measured to be sigma(tq) = 19.8(-3.1)(+3.9)(stat.)(-2.2)(+2.9)(syst.) pb and sigma((t) over barq) = 7.3(-2.1)(+3.2)(stat.)(-1.5)(+2.8)(syst.) pb. All measurements are in good agreement with the Standard Model predictions.
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Bandos, I. A., de Azcarraga, J. A., & Meliveo, C. (2011). Extended supersymmetry in massless conformal higher spin theory. Nucl. Phys. B, 853(3), 760–776.
Abstract: We propose superfield equations in tensorial N-extended superspaces to describe the N = 2,4,8 supersymmetric generalizations of free conformal higher spin theories. These can be obtained by quantizing a superparticle model in N-extended tensorial superspace. The N-extended higher spin supermultiplets just contain scalar and 'spinor' fields in tensorial space so that, in contrast with the standard (super)space approach, no nontrivial generalizations of the Maxwell or Einstein equations to tensorial space appear when N > 2. For N = 4,8, the higher spin-tensorial components of the extended tensorial superfields are expressed through additional scalar and spinor fields in tensorial space which obey the same free higher spin equations, but that are axion-like in the sense that they possess Peccei-Quinn-like symmetries.
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