Search for pair production of heavy top-like quarks decaying to a high-pT W boson and a b quark in the lepton plus jets final state in pp collisions at sqrt(s) = 8 TeV with the ATLAS detector
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2013-060/
A search is presented for production of a heavy top-like quark () together with its antiparticle, assuming a significant branching ratio for subsequent decay into a boson and a quark. The search is based on 14.3 fb of collisions at TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton+jets final state, characterised by a high-transverse-momentum isolated electron or muon, large missing transverse momentum and at least four jets, with at least one of them tagged. The analysis strategy relies on the substantial boost of the bosons in the signal when GeV. No significant excess of events above the Standard Model expectation is observed. For a chiral fourth generation quark, and under the assumption of a branching ratio , a mass lower than 740 GeV is excluded at 95% CL. For vector-like quarks, and under the assumption that only the , and decay modes contribute, 95% CL upper limits are derived for various masses in the two-dimensional plane of versus , where is the Standard Model Higgs boson. These limits are significantly improved by combining this search with a previous search for , with .