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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cantero, J., et al. (2023). A search for heavy Higgs bosons decaying into vector bosons in same-sign two-lepton final states in pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 07(7), 200–51pp.
Abstract: A search for heavy Higgs bosons produced in association with a vector boson and decaying into a pair of vector bosons is performed in final states with two leptons (electrons or muons) of the same electric charge, missing transverse momentum and jets. A data sample of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018 is used. The data correspond to a total integrated luminosity of 139 fb(-1). The observed data are in agreement with Standard Model background expectations. The results are interpreted using higher-dimensional operators in an effective field theory. Upper limits on the production cross-section are calculated at 95% confidence level as a function of the heavy Higgs boson's mass and coupling strengths to vector bosons. Limits are set in the Higgs boson mass range from 300 to 1500 GeV, and depend on the assumed couplings. The highest excluded mass for a heavy Higgs boson with the coupling combinations explored is 900 GeV. Limits on coupling strengths are also provided.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2015). Search for heavy lepton resonances decaying to a Z boson and a lepton in pp collisions at root s=8 TeV with the ATLAS detector. J. High Energy Phys., 09(9), 108–38pp.
Abstract: A search for heavy leptons decaying to a Z boson and an electron or a muon is presented. The search is based on pp collision data taken at root s = 8TeV by the ATLAS experiment at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb(-1). Three high-transverse-momentum electrons or muons are selected, with two of them required to be consistent with originating from a Z boson decay. No significant excess above Standard Model background predictions is observed, and 95% confidence level limits on the production cross section of high-mass trilepton resonances are derived. The results are interpreted in the context of vector-like lepton and type-III seesaw models. For the vector-like lepton model, most heavy lepton mass values in the range 114-176 GeV are excluded. For the type-III seesaw model, most mass values in the range 100-468 GeV are excluded.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2016). Search for heavy long-lived charged R-hadrons with the ATLAS detector in 3.2 fb(-1) of proton-proton collision data at root s=13 TeV. Phys. Lett. B, 760, 647–665.
Abstract: A search for heavy long-lived charged R-hadronsis reported using a data sample corresponding to 3.2fb(-1)of proton-proton collisions at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow propagation velocities, which are signatures of heavy charged particles travelling significantly slower than the speed of light. No significant deviations from the expected background are observed. Upper limits at 95% confidence level are provided on the production cross section of long-lived R-hadronsin the mass range from 600 GeV to 2000 GeV and gluino, bottom and top squark masses are excluded up to 1580 GeV, 805 GeV and 890 GeV, respectively.
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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 heavy long-lived multi-charged particles in the full LHC Run 2 pp collision data at √s=13 TeV using the ATLAS detector. Phys. Lett. B, 847, 138316–25pp.
Abstract: A search for heavy long-lived multi-charged particles is performed using the ATLAS detector at the LHC. Data collected in 2015-2018 at root s = 13 TeV from pp collisions corresponding to an integrated luminosity of 139 fb(-1) are examined. Particles producing anomalously high ionization, consistent with long-lived spin-1/2 massive particles with electric charges from |q| = 2e to |q| = 7e are searched for. No statistically significant evidence of such particles is observed, and 95% confidence level cross-section upper limits are calculated and interpreted as the lower mass limits for a Drell-Yan plus photon-fusion production mode. The least stringent limit, 1060 GeV, is obtained for |q| = 2e particles, and the most stringent one, 1600 GeV, is for |q| = 6e particles.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Search for heavy long-lived multicharged particles in proton-proton collisions at root s=13 TeV using the ATLAS detector. Phys. Rev. D, 99(5), 052003–26pp.
Abstract: A search for heavy long-lived multicharged particles is performed using the ATLAS detector at the LHC. Data with an integrated luminosity of 36.1 fb(-1) collected in 2015 and 2016 from proton-proton collisions at root s = 13 TeV are examined. Particles producing anomalously high ionization, consistent with long-lived massive particles with electric charges from vertical bar q vertical bar = 2e to vertical bar q vertical bar = 7e, are searched for. No events are observed, and 95% confidence level cross-section upper limits are interpreted as lower mass limits for a Drell-Yan production model. Multicharged particles with masses between 50 and 980-1220 GeV (depending on their electric charge) are excluded.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., Ferrer, A., et al. (2015). Search for heavy Majorana neutrinos with the ATLAS detector in pp collisions at root s=8 TeV. J. High Energy Phys., 07(7), 162–44pp.
Abstract: A search for heavy Majorana neutrinos in events containing a pair of high-p(T) leptons of the same charge and high-p(T) jets is presented. The search uses 20.3 fb(-1) of pp collision data collected with the ATLAS detector at the CERN Large Hadron Collider with a centre-of-mass energy of root s = 8TeV. The data are found to be consistent with the background-only hypothesis based on the Standard Model expectation. In the context of a Type-I seesaw mechanism, limits are set on the production cross-section times branching ratio for production of heavy Majorana neutrinos in the mass range between 100 and 500 GeV. The limits are subsequently interpreted as limits on the mixing between the heavy Majorana neutrinos and the Standard Model neutrinos. In the context of a left-right symmetric model, limits on the production cross-section times branching ratio are set with respect to the masses of heavy Majorana neutrinos and heavy gauge bosons W-R and Z'.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., et al. (2018). Search for additional heavy neutral Higgs and gauge bosons in the ditau final state produced in 36 fb(-1) of pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 01(1), 055–54pp.
Abstract: A search for heavy neutral Higgs bosons and Z' bosons is performed using a data sample corresponding to an integrated luminosity of 36.1 fb(-1) from proton-proton collisions at root s = 13 TeV recorded by the ATLAS detector at the LHC during 2015 and 2016. The heavy resonance is assumed to decay to tau(+)tau(-) with at least one tau lepton decaying to final states with hadrons and a neutrino. The search is performed in the mass range of 0.2-2.25 TeV for Higgs bosons and 0.2-4.0 TeV for Z' bosons. The data are in good agreement with the background predicted by the Standard Model. The results are interpreted in benchmark scenarios. In the context of the hMSSM scenario, the data exclude tan beta > 1.0 for m(A) = 0.25 TeV and tan beta > 42 for m(A) = 1.5 TeV at the 95% confidence level. For the Sequential Standard Model, Z'(SSM) with m(Z') < 2.42 TeV is excluded at 95% confidence level, while Z'(NU) with m(Z') < 2.25 TeV is excluded for the non-universal G(221) model that exhibits enhanced couplings to third-generation fermions.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Castillo, F. L., Castillo Gimenez, V., et al. (2020). Search for Heavy Higgs Bosons Decaying into Two Tau Leptons with the ATLAS Detector Using pp Collisions at root s=13 TeV. Phys. Rev. Lett., 125(5), 051801–22pp.
Abstract: A search for heavy neutral Higgs bosons is performed using the LHC Run 2 data, corresponding to an integrated luminosity of 139 fb(-1) of proton-proton collisions at root s = 13 TeV recorded with the ATLAS detector. The search for heavy resonances is performed over the mass range 0.2-2.5 TeV for the tau(+)tau(-) decay with at least one tau-lepton decaying into final states with hadrons. The data are in good agreement with the background prediction of the standard model. In the M-h(125) scenario of the minimal supersymmetric standard model, values of tan beta > 8 and tan beta > 21 are excluded at the 95% confidence level for neutral Higgs boson masses of 1.0 and 1.5 TeV, respectively, where tan beta is the ratio of the vacuum expectation values of the two Higgs doublets.
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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 heavy neutral Higgs bosons produced in association with b-quarks and decaying into b-quarks at root s=13 TeV with the ATLAS detector. Phys. Rev. D, 102(3), 032004–31pp.
Abstract: A search for heavy neutral Higgs bosons produced in association with one or two b-quarks and decaying to b-quark pairs is presented using 27.8 fb(-1) of root s=13 TeV proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider during 2015 and 2016. No evidence of a signal is found. Upper limits on the heavy neutral Higgs boson production cross section times its branching ratio to b (b) over bar are set, ranging from 4.0 to 0.6 pb at 95% confidence level over a Higgs boson mass range of 450 to 1400 GeV. Results are interpreted within the two-Higgs-doublet model and the minimal supersymmetric Standard Model.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Search for Heavy Higgs Bosons A/H Decaying to a Top Quark Pair in pp Collisions at root s=8 TeV with the ATLAS Detector. Phys. Rev. Lett., 119(19), 191803–20pp.
Abstract: A search for heavy pseudoscalar (A) and scalar (H) Higgs bosons decaying into a top quark pair (t (t) over bar) has been performed with 20.3 fb(-1) of proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider at a center-of-mass energy root s = 8 TeV. Interference effects between the signal process and standard model t (t) over bar production, which are expected to distort the signal shape from a single peak to a peak-dip structure, are taken into account. No significant deviation from the standard model prediction is observed in the t (t) over bar invariant mass spectrum in final states with an electron or muon, large missing transverse momentum, and at least four jets. The results are interpreted within the context of a type-II two-Higgs-doublet model. Exclusion limits on the signal strength are derived as a function of the mass m(A/H) and the ratio of the vacuum expectation values of the two Higgs fields, tan beta, for m(A/H) > 500 GeV.
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