Search for pair production of heavy vector-like quarks decaying into high-$p_T$ $W$ bosons and top quarks in the lepton-plus-jets final state in $pp$ collisions at $\sqrt{s}$=13 TeV with the ATLAS detector

The ATLAS collaboration
No Journal Information, 2018

Abstract (data abstract)
CERN-LHC, ATLAS. Limits on pair production of a heavy vector-like B quark together with its antiparticle, where the B quark decays to a W boson and a top quark. The search is based on 36.1 +\- 0.8 fb^{-1} of pp collisions at sqrt{s} = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton plus jets final state, including at least four small jets out of which at least one is required to be b-tagged jet and a large-radius jet. Mass limits on B production are set as a function of the decay branching ratios. Basic event selection: - ==1 electron or muon: pT >= 30 GeV, in fiducial volume, isolated from jets - Missing transverse momentum >= 60 GeV - >=4 small-R jets, with at least one b-tagged - >=1 large-radius jet - S_T > 1200 GeV Comment: Leptonically and hadronically decaying VLQ candidates are reconstructed (see paper) . Additional selection: Signal region 1 (RECOSR): - >=3 large-radius jets - >=1 hadronic W candidate: W-tagged large-R jet not overlapping with a b-tagged jet - S_T >= 1500 GeV - Delta R(lepton, p_T leading b-jet) >= 1 Comment: Final discriminant is the mass of the hadronically decaying VLB candidate Signal region 2 (BDTSR): - S_T >= 1200 GeV - RECOSR veto Comment: Final discriminant is the BDT discriminant

  • Table 0: Final Variable Distribution (RECOSR)

    Data from Figure 3a

    10.17182/hepdata.83104.v1/t1

    The hadronically decaying VLB candidate mass in the RECOSR region after the maximum likelihood fit in the two signal regions...

  • Table 1: Final Variable Distribution (BDTSR)

    Data from Figure 3b

    10.17182/hepdata.83104.v1/t2

    The BDT discriminant in the BDTSR region after the maximum likelihood fit in the two signal regions overlayed with the...

  • Table 2: BB->WtWt Cross Section Limit

    Data from Figure 4a

    10.17182/hepdata.83104.v1/t3

    Expected and observed upper limits at the 95% CL on the BB cross section as a function of B quark...

  • Table 3: SU(2) Singlet Cross Section Limit

    Data from Figure 4b

    10.17182/hepdata.83104.v1/t4

    Expected and observed upper limits at the 95% CL on the BB cross section as a function of B quark...

  • Table 4: Limit on B mass vs. BR

    Data from Figure 5

    10.17182/hepdata.83104.v1/t5

    Expected and observed 95% CL lower limits on the mass of the B quark in the branching ratio plane of...

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