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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Castillo, F. L., et al. (2020). Search for squarks and gluinos in final states with same-sign leptons and jets using 139 fb(-1) of data collected with the ATLAS detector. J. High Energy Phys., 06(6), 046–44pp.
Abstract: A search for supersymmetric partners of gluons and quarks is presented, involving signatures with jets and either two isolated leptons (electrons or muons) with the same electric charge, or at least three isolated leptons. A data sample of proton-proton collisions at root s = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to a total integrated luminosity of 139 fb(-1), is used for the search. No significant excess over the Standard Model expectation is observed. The results are interpreted in simplified supersymmetric models featuring both R-parity conservation and R-parity violation, raising the exclusion limits beyond those of previous ATLAS searches to 1600 GeV for gluino masses and 750 GeV for bottom and top squark masses in these scenarios.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., Castillo, F. L., et al. (2021). Search for supersymmetry in events with four or more charged leptons in 139 fb(-1) of root s=13 TeV pp collisions with the ATLAS detector. J. High Energy Phys., 07(7), 167–57pp.
Abstract: A search for supersymmetry in events with four or more charged leptons (electrons, muons and tau-leptons) is presented. The analysis uses a data sample corresponding to 139 fb(-1) of proton-proton collisions delivered by the Large Hadron Collider at root s = 13 TeV and recorded by the ATLAS detector. Four-lepton signal regions with up to two hadronically decaying tau-leptons are designed to target several supersymmetric models, while a general five-lepton signal region targets any new physics phenomena leading to a final state with five charged leptons. Data yields are consistent with Standard Model expectations and results are used to set upper limits on contributions from processes beyond the Standard Model. Exclusion limits are set at the 95% confidence level in simplified models of general gauge-mediated supersymmetry, excluding higgsino masses up to 540 GeV. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to charged leptons, lower limits of 1.6 TeV, 1.2 TeV, and 2.5 TeV are placed on wino, slepton and gluino masses, respectively.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo, F. L., et al. (2019). Search for squarks and gluinos in final states with hadronically decaying tau-leptons, jets, and missing transverse momentum using pp collisions at root s=13 TeV with the ATLAS detector. Phys. Rev. D, 99(1), 012009–34pp.
Abstract: A search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying tau-lepton is presented. Two exclusive final states with either exactly one or at least two tau-leptons are considered. The analysis is based on proton-proton collisions at root s = 13 TeV corresponding to an integrated luminosity of 36.1 fb(-1) delivered by the Large Hadron Collider and recorded by the ATLAS detector in 2015 and 2016. No significant excess is observed over the Standard Model expectation. At 95% confidence level, model-independent upper limits on the cross section are set and exclusion limits are provided for two signal scenarios: a simplified model of gluino pair production with tau-rich cascade decays, and a model with gauge-mediated supersymmetry breaking (GMSB). In the simplified model, gluino masses up to 2000 GeV are excluded for low values of the mass of the lightest supersymmetric particle (LSP), while LSP masses up to 1000 GeV are excluded for gluino masses around 1400 GeV. In the GMSB model, values of the supersymmetry-breaking scale are excluded below 110 TeV for all values of tan beta in the range 2 <= tan beta <= 60, and below 120 TeV for tan beta > 30.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2023). Search for supersymmetry in final states with missing transverse momentum and three or more b-jets in 139 fb-1 of proton-proton collisions at √s=13 TeV with the ATLAS detector. Eur. Phys. J. C, 83(7), 561–41pp.
Abstract: A search for supersymmetry involving the pair production of gluinos decaying via off-shell third-generation squarks into the lightest neutralino ((chi) over tilde (0)(1)) is reported. It exploits LHC proton-proton collision data at a centre-ofmass energy root s = 13 TeV with an integrated luminosity of 139 fb(-1) collected with the ATLAS detector from 2015 to 2018. The search uses events containing large missing transverse momentum, up to one electron or muon, and several energetic jets, at least three of which must be identified as containing b-hadrons. Both a simple kinematic event selection and an event selection based upon a deep neural network are used. No significant excess above the predicted background is found. In simplified models involving the pair production of gluinos that decay via off-shell top (bottom) squarks, gluino masses less than 2.44 TeV (2.35 TeV) are excluded at 95% CL for a massless (chi) over tilde (0)(1). Limits are also set on the gluino mass in models with variable branching ratios for gluino decays to b (b) over bar (chi) over tilde (0)(1), t (t) over bar (chi) over tilde (0)(1) and t (b) over bar (chi) over tilde (-)(iota) / (t) over barb (chi) over tilde (0)(1).
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2023). Search for direct production of winos and higgsinos in events with two same-charge leptons or three leptons in pp collision data at √s=13 TeV with the ATLAS detector. J. High Energy Phys., 11(11), 150–70pp.
Abstract: A search for supersymmetry targeting the direct production of winos and higgsinos is conducted in final states with either two leptons (e or mu) with the same electric charge, or three leptons. The analysis uses 139 fb(-1) of pp collision data at root s = 13TeV collected with the ATLAS detector during Run 2 of the Large Hadron Collider. No significant excess over the Standard Model expectation is observed. Simplified and complete models with and without R-parity conservation are considered. In topologies with intermediate states including either Wh or WZ pairs, wino masses up to 525 GeV and 250 GeV are excluded, respectively, for a bino of vanishing mass. Higgsino masses smaller than 440 GeV are excluded in a natural R-parity-violating model with bilinear terms. Upper limits on the production cross section of generic events beyond the Standard Model as low as 40 ab are obtained in signal regions optimised for these models and also for an R-parity-violating scenario with baryon-number-violating higgsino decays into top quarks and jets. The analysis significantly improves sensitivity to supersymmetric models and other processes beyond the Standard Model that may contribute to the considered final states.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Castillo, F. L., et al. (2020). Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in root s=13 TeV pp collisions with the ATLAS detector. Phys. Rev. D, 101(7), 072001–32pp.
Abstract: A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of root s = 13 TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb(-1). A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015-2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Observation of the Bs0 -> (DD -/+)-D-*+/- decay. J. High Energy Phys., 03(3), 099–19pp.
Abstract: A search for the B-s(0) -> D*(+/-) D--/+ decay is performed using proton-proton collision data at centre-of-mass energies of 7, 8 and 13TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1). The decay is observed with a high significance and its branching fraction relative to the B-0 -> D*(+/-) D--/+ decay is measured to be B(B-s(0) -> D*D-+/-(-/+))/B(B-0 -> D*D-+/-(-/+)) = 0.137 +/- 0.017 +/- 0.002 +/- 0.006, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the B-s(0) and B-0 hadronisation fractions.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Search for the baryon- and lepton-number violating decays B0 → pμ- and Bs0 → pμ-. Phys. Rev. D, 108(1), 012021–15pp.
Abstract: A search for the baryon- and lepton-number violating decays B-0 -> p mu(-) and B-s(0) -> p mu(-) is performed at the LHCb experiment using data collected in proton-proton collisions at root s = 7, 8 and 13 TeV, corresponding to integrated luminosities of 1, 2, and 6 fb(-1), respectively. No significant signal for B-0 -> p mu(-) and B-s(0) -> p mu(-) decays is found and the upper limits on the branching fractions are determined to be B(B-0 -> p mu(-)) < 2.6(3.1) x 10(-9) and B(B-s(0) -> p mu(-)) < 12.1(14.0) x 10(-9), respectively, at 90% (95%) confidence level. These are the first limits on these decays to date.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., et al. (2023). Search for the charged-lepton-flavor-violating decay Z → eμ in pp collisions at √s=13 TeV with the ATLAS detector. Phys. Rev. D, 108(3), 032015–22pp.
Abstract: A search for the charged-lepton-flavor-violating process Z -> e μis presented, using 139 fb(-1) of root s = 13 TeV pp collision data collected by the ATLAS experiment at the LHC. An excess in the e μinvariant mass spectrum near the Z boson mass would be a striking signature of new physics. No excess is observed, and an upper limit B(Z -> e mu) < 2.62 x 10(-7) is placed on the branching fraction at 95% confidence level, which is the most stringent limit to date.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Search for the decay B-0 -> phi mu(+) mu(-). J. High Energy Phys., 05(5), 067–21pp.
Abstract: A search for the decay B-0 -> phi mu(+) mu(-) is performed using proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV collected by the LHCb experiment and corresponding to an integrated luminosity of 9 fb(-1). No evidence for the B-0 -> phi mu(+) mu(-) decay is found and an upper limit on the branching fraction, excluding the 0 and charmonium regions in the dimuon spectrum, of 4.4 x 10(-3) at a 90% credibility level, relative to that of the B-s(0) -> phi mu(+) mu(-) decay, is established. Using the measured B-s(0) -> phi mu(+) mu(-) branching fraction and assuming a phase-space model, the absolute branching fraction of the decay B-0 -> phi mu(+) mu(-) in the full q(2) range is determined to be less than 3.2 x 10(-9) at a 90% credibility level.
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