Yazar "Uysal, Zekeriya" seçeneğine göre listele
Listeleniyor 1 - 20 / 25
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Calibration of a soft secondary vertex tagger using proton-proton collisions at Formula Presented with the ATLAS detector(American physical society, 2024) Aad, G.; Aakvaag, E.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, Zekeriya; Çelebi, EmreSeveral processes studied by the ATLAS experiment at the Large Hadron Collider produce low-momentum Formula Presented-flavored hadrons in the final state. This paper describes the calibration of a dedicated tagging algorithm that identifies Formula Presented-flavored hadrons outside of hadronic jets by reconstructing the soft secondary vertices originating from their decays. The calibration is based on a proton-proton collision dataset at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of Formula Presented. Scale factors used to correct the algorithm’s performance in simulated events are extracted for the Formula Presented-tagging efficiency and the mistag rate of the algorithm using a data sample enriched in Formula Presented events. Several orthogonal measurement regions are defined, binned as a function of the multiplicities of soft secondary vertices and jets containing a Formula Presented-flavored hadron in the event. The mistag rate scale factors are estimated separately for events with low and high average numbers of interactions per bunch crossing. The results, which are derived from events with low missing transverse momentum, are successfully validated in a phase space characterized by high missing transverse momentum and therefore are applicable to new physics searches carried out in either phase space regime.Öğe Combination of measurements of the top quark mass from data collected by the ATLAS and CMS Experiments at √=7 and 8 TeV(American physical society, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaA combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The datasets used correspond to an integrated luminosity of up to 5 and Formula Presented of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak Formula Presented channel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is Formula Presented, with a total uncertainty of 0.33 GeV.Öğe Combination of searches for Higgs boson decays into a photon and a massless dark photon using pp collisions at s= 13 TeV with the ATLAS detector(Springer science and business media deutschland GmbH, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Çelebi, Emre; Şimşek, Sinem; Uysal, Zekeriya; Öztürk, Sertaç; Şahinsoy, MerveA combination of searches for Higgs boson decays into a visible photon and a massless dark photon (H → γγd) is presented using 139 fb−1 of proton-proton collision data at a centre-of-mass energy of s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The observed (expected) 95% confidence level upper limit on the Standard Model Higgs boson decay branching ratio is determined to be B(H → γγd) < 1.3% (1.5)%. The search is also sensitive to higher-mass Higgs bosons decaying into the same final state. The observed (expected) 95% confidence level limit on the cross-section times branching ratio ranges from 16 fb (20 fb) for mH = 400 GeV to 1.0 fb (1.5 fb) for mH = 3 TeV. Results are also interpreted in the context of a minimal simplified model.Öğe Combination of searches for pair-produced leptoquarks at s=13 TeV with the ATLAS detector(Elsevier, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Şimşek, Sinem; Uysal, Zekeriya; Öztürk, SertaçA 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 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.Öğe Combination of searches for resonant higgs boson pair production using 𝑝𝑝 collisions at √𝑠=13 TeV with the ATLAS detector(American Physical Society, 2024) Filmer, E.K.; Grant, C.M.; Jackson, P; Beddal, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaA combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to Formula Presented of Formula Presented collision data at Formula Presented recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: Formula Presented, Formula Presented, and Formula Presented. No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating from the decay of a narrow scalar resonance with mass in the range 251 GeV-5 TeV. The observed (expected) limits are in the range 0.96-600 fb (1.2-390 fb). The limits are interpreted in the type-I two-Higgs-doublet model and the minimal supersymmetric standard model, and constrain parameter space not previously excluded by other searches. © 2024 CERN, for the ATLAS Collaboration.Öğe Combination of searches for singly and doubly charged Higgs bosons produced via vector-boson fusion in proton–proton collisions at s=13 TeV with the ATLAS detector(Elsevier b.v., 2025) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Çelebi, Emre; Şimşek, Sinem; Uysal, Zekeriya; Öztürk, Sertaç; Şahinsoy, MerveA combination of searches for singly and doubly charged Higgs bosons, H-+/- and H-+/-+/-, produced via vector-boson fusion is performed using 140 fb(-1) of proton-proton collisions at a centre-of-mass energy of 13 TeV, collected with the ATLAS detector during Run 2 of the Large Hadron Collider. Searches targeting decays to massive vector bosons in leptonic final states (electrons or muons) are considered. New constraints are reported on the production crosssection times branching fraction for charged Higgs boson masses between 200 GeV and 3000 GeV. The results are interpreted in the context of the Georgi-Machacek model for which the most stringent constraints to date are set for the masses considered in the combination.Öğe Constraint on the total width of the Higgs boson from Higgs boson and four-top-quark measurements in pp collisions at = 13 TeV with the ATLAS detector(Elsevier B.V., 2025) Aad, G.; Aakvaag, E.; Abbott, B.; Beddall, Andrew John; Çelebi,; Öztürk, Sertaç; Şahinsoy, Merve; Şimşek, Sinem; Uysal, ZekeriyaThis Letter presents a constraint on the total width of the Higgs boson (ΓH) using a combined measurement of on-shell Higgs boson production and the production of four top quarks, which involves contributions from off-shell Higgs boson-mediated processes. This method relies on the assumption that the tree-level Higgs-top Yukawa coupling strength is the same for on-shell and off-shell Higgs boson production processes, thereby avoiding any assumptions about the relationship between on-shell and off-shell gluon fusion Higgs production rates, which were central to previous measurements. The result is based on up to 140 fb−1 of proton–proton collisions at a centre-of-mass energy of s = 13 TeV collected with the ATLAS detector at the Large Hadron Collider. The observed (expected) 95% confidence level upper limit on ΓH is 450 MeV (75 MeV). Additionally, considering the constraint on the Higgs-top Yukawa coupling from loop-induced Higgs boson production and decay processes further yields an observed (expected) upper limit of 160 MeV (55 MeV). © 2025 CERN for the benefit of the ATLAS CollaborationÖğe Inclusive and differential cross-section measurements of tt¯Z production in pp collisions at s = 13 TeV with the ATLAS detector, including EFT and spin-correlation interpretations(Springer Science and Business Media Deutschland GmbH, 2024) G, Aad; B, Abbott; K, Abeling; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaMeasurements of both the inclusive and differential production cross sections of a top-quark-top-antiquark pair in association with a Z boson (tt¯Z) are presented. Final states with two, three or four isolated leptons (electrons or muons) are targeted. The measurements use the data recorded by the ATLAS detector in pp collisions at s = 13 TeV at the Large Hadron Collider during the years 2015–2018, corresponding to an integrated luminosity of 140 fb−1. The inclusive cross section is measured to be σtt¯Z = 0.86 ± 0.04 (stat.) ± 0.04 (syst.) pb and found to be in agreement with the most advanced Standard Model predictions. The differential measurements are presented as a function of a number of observables that probe the kinematics of the tt¯Z system. Both the absolute and normalised differential cross-section measurements are performed at particle level and parton level for specific fiducial volumes, and are compared with NLO+NNLL theoretical predictions. The results are interpreted in the framework of Standard Model effective field theory and used to set limits on a large number of dimension-6 operators involving the top quark. The first measurement of spin correlations in tt¯Z events is presented: the results are in agreement with the Standard Model expectations, and the null hypothesis of no spin correlations is disfavoured with a significance of 1.8 standard deviations. © The Author(s) 2024.Öğe Measurement of the VH,H → ττ process with the ATLAS detector at 13 TeV(Elsevier B.V., 2024) Aad, G.; Aakvaag, E.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaA measurement of the Standard Model Higgs boson produced in association with a W or Z boson and decaying into a pair of τ-leptons is presented. This search is based on proton-proton collision data collected at s=13 TeV by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 140 fb−1. For the Higgs boson candidate, only final states with at least one τ-lepton decaying hadronically (τ→hadrons+ντ) are considered. For the vector bosons, only leptonic decay channels are considered: Z→ℓℓ and W→ℓνℓ, with ℓ=e,μ. An excess of events over the expected background is found with an observed (expected) significance of 4.2 (3.6) standard deviations, providing evidence of the Higgs boson produced in association with a vector boson and decaying into a pair of τ-leptons. The ratio of the measured cross-section to the Standard Model prediction is μVHττ=1.28−0.29+0.30(stat.)−0.21+0.25(syst.). This result represents the most accurate measurement of the VH(ττ) process achieved to date. © 2024 The Author(s)Öğe Measurement of top-quark pair production in association with charm quarks in proton–proton collisions at s=13 TeV with the ATLAS detector(Elsevier b.v., 2025) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Çelebi, Emre; Şimşek, Sinem; Uysal, Zekeriya; Öztürk, Sertaç; Şahinsoy, Merve; Petukhov, AleksandrInclusive cross-sections for top-quark pair production in association with charm quarks are measured with proton–proton collision data at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 140 fb−1, collected with the ATLAS experiment at the LHC between 2015 and 2018. The measurements are performed by requiring one or two charged leptons (electrons and muons), two b-tagged jets, and at least one additional jet in the final state. A custom flavor-tagging algorithm is employed for the simultaneous identification of b-jets and c-jets. In a fiducial phase space that replicates the acceptance of the ATLAS detector, the cross-sections for tt¯+≥2c and tt¯+1c production are measured to be 1.28−0.24+0.27pb and 6.4−0.9+1.0pb, respectively. The measurements are primarily limited by uncertainties in the modeling of inclusive tt¯ and tt¯+bb¯ production, in the calibration of the flavor-tagging algorithm, and by data statistics. Cross-section predictions from various tt¯ simulations are largely consistent with the measured cross-section values, though all underpredict the observed values by 0.5 to 2.0 standard deviations. In a phase-space volume without requirements on the tt¯ decay products and the jet multiplicity, the cross-section ratios of tt¯+≥2c and tt¯+1c to total tt¯+jets production are determined to be (1.23±0.25)% and (8.8±1.3)%.Öğe Measurement of vector boson production cross sections and their ratios using pp collisions at √s=13.6 TeV with the ATLAS detector(Elsevier, 2024) Aad, G.; Aakvaag, E.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaFiducial and total W+ and Z boson cross sections, their ratios and the ratio of top-antitop-quark pair and.. -boson fiducial cross sections are measured in proton-proton collisions at a centre-of-mass energy of root s = 13.6 TeV, corresponding to an integrated luminosity of 29 fb(-1) of data collected in 2022 by the ATLAS experiment at the Large Hadron Collider. The measured fiducial cross-section values for W+ -> l(+) v, W- -> l(-) v- , and Z -> l(+)l(-) (l =e or mu) boson productions are 4250 +/- 150 pb, 3310 +/- 120 pb, and 744 +/- 20 pb, respectively, where the uncertainty is the total uncertainty, including that arising from the luminosity of about 2.2%. The measurements are in agreement with Standard-Model predictions calculated at next-to-next-to-leading-order in alpha(s) ,next-to-nextto-leading logarithmic accuracy and next-to-leading-order electroweak accuracy.Öğe Measurement of ZZ production cross-sections in the four-lepton final state in pp collisions at s=13.6TeV with the ATLAS experiment(Elsevier B.V., 2024) Aad, G.; Abbott, B.; Abeling, K.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaThis paper reports cross-section measurements of ZZ production in pp collisions at s=13.6TeV at the Large Hadron Collider. The data were collected by the ATLAS detector in 2022, and correspond to an integrated luminosity of 29 fb−1. Events in the ZZ→4ℓ (ℓ=e, μ) final states are selected and used to measure the inclusive and differential cross-sections in a fiducial region defined close to the analysis selections. The inclusive cross-section is further extrapolated to the total phase space with a requirement of 66Öğe Performance of the ATLAS forward proton time-of-Flight detector in run 2(Institute of physics, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaWe present performance studies of the Time-of-Flight (ToF) subdetector of the ATLAS Forward Proton (AFP) detector at the LHC. Efficiencies and resolutions are measured using high-statistics data samples collected at low and moderate pile-up in 2017, the first year when the detectors were installed on both sides of the interaction region. While low efficiencies are observed, of the order of a few percent, the resolutions of the two ToF detectors measured individually are 21 ps and 28 ps, yielding an expected resolution of the longitudinal position of the interaction, z vtx, in the central ATLAS detector of 5.3 ± 0.6 mm. This is in agreement with the observed width of the distribution of the difference between z vtx, measured independently by the central ATLAS tracker and by the ToF detector, of 6.0 ± 2.0 mm.Öğe Search for charged-lepton-flavor violating 𝜇𝜏𝑞𝑡 interactions in top-quark production and decay in 𝑝𝑝 collisions at √𝑠=13 TeV with the ATLAS detector at the LHC(American physical society, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaA search for charged-lepton-flavor violating Formula Presented (Formula Presented, Formula Presented) interactions is presented, considering both top-quark production and decay. The data analyzed correspond to Formula Presented of proton-proton collisions at a center-of-mass energy of Formula Presented recorded with the ATLAS detector at the Large Hadron Collider. The analysis targets events containing two muons with the same electric charge, a hadronically decaying Formula Presented-lepton and at least one jet, with exactly one Formula Presented-tagged jet, produced by a Formula Presented interaction. Agreement with the Standard Model expectation within 1.6 standard deviations is observed, and limits are set at the 95% confidence level (CL) on the charged-lepton-flavor violation branching ratio of Formula Presented. An effective field theory interpretation is performed yielding 95% CL limits on Wilson coefficients, dependent on the flavor of the associated light quark and the Lorentz structure of the coupling. These range from Formula Presented for Formula Presented to Formula Presented for Formula Presented. An additional interpretation is performed for scalar leptoquark production inducing charged-lepton-flavor violation, with fixed intergenerational couplings. Upper limits on leptoquark coupling strengths are set at the 95% CL, ranging from Formula Presented to Formula Presented for leptoquark masses between 0.5 and 2.0 TeV.Öğe Search for flavour-changing neutral-current couplings between the top quark and the Higgs boson in multi-lepton final states in 13 TeV pp collisions with the ATLAS detector(Springer, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaA search is presented for flavour-changing neutral-current interactions involving the top quark, the Higgs boson and an up-type quark (q=u,c) with the ATLAS detector at the Large Hadron Collider. The analysis considers leptonic decays of the top quark along with Higgs boson decays into two W bosons, two Z bosons or a τ+τ- pair. It focuses on final states containing either two leptons (electrons or muons) of the same charge or three leptons. The considered processes are tt¯ and Ht production. For the tt¯ production, one top quark decays via t→Hq. The proton–proton collision data set analysed amounts to (140fb-1) at (s=13TeV). No significant excess beyond Standard Model expectations is observed and upper limits are set on the t→Hq branching ratios at 95 % confidence level, amounting to observed (expected) limits of B(t→Hu)<2.8(3.0)×10-4 and B(t→Hc)<3.3(3.8)×10-4. Combining this search with other searches for tHq flavour-changing neutral-current interactions previously conducted by ATLAS, considering H→bb¯ and H→γγ decays, as well as H→τ+τ- decays with one or two hadronically decaying τ-leptons, yields observed (expected) upper limits on the branching ratios of B(t→Hu)<2.6(1.8)×10-4 and B(t→Hc)<3.4(2.3)×10-4.Öğe Search for heavy Majorana neutrinos in e±e± and e±μ± final states via WW scattering in pp collisions at s=13 TeV with the ATLAS detector(Elsevier, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Çelebi, Emre; Şimşek, Sinem; Uysal, Zekeriya; Öztürk, Sertaç; Şahinsoy, MerveA search for heavy Majorana neutrinos in scattering of same-sign W boson pairs in proton–proton collisions at s=13 TeV at the LHC is reported. The dataset used corresponds to an integrated luminosity of 140 fb−1, collected with the ATLAS detector during 2015–2018. The search is performed in final states including a same-sign ee or eμ pair and at least two jets with large invariant mass and a large rapidity difference. No significant excess of events with respect to the Standard Model background predictions is observed. The results are interpreted in a benchmark scenario of the Phenomenological Type-I Seesaw model. New constraints are set on the values of the |VeN|2 and |VeNVμN⁎| parameters for heavy Majorana neutrino masses between 50 GeV and 20 TeV, where VℓN is the matrix element describing the mixing of the heavy Majorana neutrino mass eigenstate with the Standard Model neutrino of flavour ℓ=e,μ. The sensitivity to the Weinberg operator is investigated and constraints on the effective ee and eμ Majorana neutrino masses are reported. The statistical combination of the ee and eμ channels with the previously published μμ channel is performed.Öğe Search for low-mass resonances decaying into two jets and produced in association with a photon or a jet at Formula Presented with the ATLAS detector(American physical society, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaA search is performed for localized excesses in the low-mass dijet invariant mass distribution, targeting a hypothetical new particle decaying into two jets and produced in association with either a high transverse momentum photon or a jet. The search uses the full Run 2 data sample from LHC proton-proton collisions collected by the ATLAS experiment at a center-of-mass energy of 13 TeV during 2015-2018. Two variants of the search are presented for each type of initial-state radiation: one that makes no jet flavor requirements and one that requires both of the jets to have been identified as containing Formula Presented-hadrons. No excess is observed relative to the Standard Model prediction, and the data are used to set upper limits on the production cross section for a benchmark Formula Presented model and, separately, for generic, beyond the Standard Model scenarios which might produce a Gaussian-shaped contribution to dijet invariant mass distributions. The results extend the current constraints on dijet resonances to the mass range between 200 and 650 GeV.Öğe Search for new particles in final states with a boosted top quark and missing transverse momentum in proton-proton collisions at s = 13 TeV with the ATLAS detector(Springer science and business media deutschland GmbH, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Şimşek, Sinem; Uysal, ZekeriyaA search for events with one top quark and missing transverse momentum in the final state is presented. The fully hadronic decay of the top quark is explored by selecting events with a reconstructed boosted top-quark topology produced in association with large missing transverse momentum. The analysis uses 139 fb−1 of proton-proton collision data at a centre-of-mass energy of s = 13 TeV recorded during 2015-2018 by the ATLAS detector at the Large Hadron Collider. The results are interpreted in the context of simplified models for Dark Matter particle production and the single production of a vector-like T quark. Without significant excess relative to the Standard Model expectations, 95% confidence-level upper limits on the corresponding cross-sections are obtained. The production of Dark Matter particles in association with a single top quark is excluded for masses of a scalar (vector) mediator up to 4.3 (2.3) TeV, assuming mχ = 1 GeV and the model couplings λq = 0.6 and λχ = 0.4 (a = 0.5 and gχ = 1). The production of a single vector-like T quark is excluded for masses below 1.8 TeV assuming a coupling to the top quark κT = 0.5 and a branching ratio for T → Zt of 25%.Öğe Search for non-resonant Higgs boson pair production in final states with leptons, taus, and photons in pp collisions at √s = 13 TeV with the ATLAS detector(Springer science and business media deutschland GmbH, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Çelebi, Emre; Şimşek, Sinem; Uysal, ZekeriyaA search is presented for non-resonant Higgs boson pair production, targeting the bbZZ, 4V (V = W or Z), VVττ, 4τ, γγVV and γγττ decay channels. Events are categorised based on the multiplicity of light charged leptons (electrons or muons), hadronically decaying tau leptons, and photons. The search is based on a data sample of proton-proton collisions at s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb−1. No evidence of the signal is found and the observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 17 (11) times the Standard Model predicted cross-section at 95% confidence level under the background-only hypothesis. The observed (expected) constraints on the HHH coupling modifier, κλ, are determined to be −6.2 < κλ< 11.6 (−4.5 < κλ< 9.6) at 95% confidence level, assuming the Standard Model for the expected limits and that new physics would only affect κλ.Öğe 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(Elsevier, 2024) Aad, G.; Abbott, B.; Beddall, Andrew John; Çetin, Serkant Ali; Öztürk, Sertaç; Şimşek, Sinem; Uysal, ZekeriyaA 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.
