Search for pair production of heavy top-like quarks decaying to a high-pTW boson and a b quark in the lepton plus jets final state at s=7TeV 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=7TeV 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'?400GeV. 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 656GeV is excluded at 95% confidence level. In addition, in light of the recent discovery of a new boson of mass ~126GeV 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. © 2012 CERN.
Aad, G; Abajyan, T; Abbott, B; Abdallah, J; Abdel Khalek, S; Abdelalim, AA; Abdinov, O; Aben, R; Abi, B; Abolins, M; AbouZeid, OS; Abramowicz, H; Abreu, H; Acharya, BS; Adamczyk, L; Adams, DL; Addy, TN; Adelman, J; Adomeit, S; Adragna, P; Adye, T; Aefsky, S; Aguilar-Saavedra, JA; Agustoni, M; Aharrouche, M; Ahlen, SP; Ahles, F; Ahmad, A; Ahsan, M; Aielli, G; A kesson, TPA; Akimoto, G; Akimov, AV; Alam, MS; Alam, MA; Albert, J; Albrand, S; Aleksa, M; Aleksandrov, IN; Alessandria, F; Alexa, C; Alexander, G; Alexandre, G; Alexopoulos, T; Alhroob, M; Aliev, M; Alimonti, G; Alison, J; Allbrooke, BMM; Allport, PP; Allwood-Spiers, SE; Almond, J; Aloisio, A; Alon, R; Alonso, A; Alonso, F; Altheimer, A; Alvarez Gonzalez, B; Alviggi, MG; Amako, K; Amelung, C; Ammosov, VV; Amor Dos Santos, SP; Amorim, A; Amram, N; Anastopoulos, C; Ancu, LS; Andari, N; Andeen, T; Anders, CF; Anders, G; Anderson, KJ; Andreazza, A; Andrei, V; Andrieux, ML; Anduaga, XS; Angelidakis, S; Anger, P; Angerami, A; Anghinolfi, F; Anisenkov, A; Anjos, N; Annovi, A; Antonaki, A; Antonelli, M; Antonov, A; Antos, J; Anulli, F; Aoki, M; Aoun, S; Aperio Bella, L; Apolle, R
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