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 at $\sqrt{s}$=7 TeV with the ATLAS detector

A search is presented for production of a heavy up-type quark ( t′ ) together with its antiparticle, assuming a significant branching ratio for subsequent decay into a W boson and a b quark. The search is based on 4.7 fb −1 of pp collisions at s=7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton + jets final state, characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum and at least three jets. The analysis strategy relies on the substantial boost of the W bosons in the t′t¯′ signal when mt′≳400 GeV . No significant excess of events above the Standard Model expectation is observed and the result of the search is interpreted in the context of fourth-generation and vector-like quark models. Under the assumption of a branching ratio BR(t′→Wb)=1 , a fourth-generation t′ quark with mass lower than 656 GeV is excluded at 95% confidence level. In addition, in light of the recent discovery of a new boson of mass ∼126 GeV at the LHC, upper limits are derived in the two-dimensional plane of BR(t′→Wb) versus BR(t′→Ht) , where H is the Standard Model Higgs boson, for vector-like quarks of various masses.

Note:

11 pages plus author list (26 pages total), 4 figures, 1 table, submitted to Physics Letters B

p p: interaction
new particle: search for
top': pair production
top': decay modes
final state: ((n)jet lepton)
lepton: transverse momentum
transverse energy: missing-energy
top': mass
top': vector particle
family: 4

References(61)

Figures(7)

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D0

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