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  • Measurement of $t \bar{t}$ production with a veto on additional central jet activity in pp collisions at sqrt(s) = 7 TeV using the ATLAS detector
    Publication . ATLAS collaboration (3054 authors); Aguilar-Saavedra, Juan Antonio; Amaral, Pedro; Anjos, Nuno; Carvalho, João; Castro, Nuno Filipe; Conde Muiño, Patricia; Do Valle Wemans, André; Fiolhais, Miguel; Gomes, Agostinho; Gonçalo, Ricardo; Jorge, Pedro; Lopes, Lourenco; Machado Miguens, Joana; Maio, Amélia; Maneira, José; Oliveira, Miguel Alfonso; Onofre, António; Palma, Alberto; Pina, João Antonio; Pinto, Belmiro; Santos, Helena; Saraiva, João; Silva, José; Soares, Mara; Veloso, Filipe; Wolters, Helmut
    A measurement of the jet activity in ttbar events produced in proton-proton collisions at a centre-of-mass energy of 7 TeV is presented, using 2.05 fb^-1 of integrated luminosity collected by the ATLAS detector at the Large Hadron Collider. The ttbar events are selected in the dilepton decay channel with two identified b-jets from the top quark decays. Events are vetoed if they contain an additional jet with transverse momentum above a threshold in a central rapidity interval. The fraction of events surviving the jet veto is presented as a function of this threshold for four different central rapidity interval definitions. An alternate measurement is also performed, in which events are vetoed if the scalar transverse momentum sum of the additional jets in each rapidity interval is above a threshold. In both measurements, the data are corrected for detector effects and compared to the theoretical models implemented in MC@NLO, POWHEG, ALPGEN and SHERPA. The experimental uncertainties are often smaller than the spread of theoretical predictions, allowing deviations between data and theory to be observed in some regions of phase space.
    2012-06-21Journal article Open access Show more
  • Measurement of the top quark mass with the template method in the $t \bar{t}$ -> lepton + jets channel using ATLAS data
    Publication . ATLAS collaboration (3033 authors); Aguilar-Saavedra, Juan Antonio; Amaral, Pedro; Anjos, Nuno; Carvalho, João; Castro, Nuno Filipe; Conde Muiño, Patricia; Do Valle Wemans, André; Fiolhais, Miguel; Gomes, Agostinho; Gonçalo, Ricardo; Jorge, Pedro; Lopes, Lourenco; Machado Miguens, Joana; Maio, Amélia; Maneira, José; Oliveira, Miguel Alfonso; Onofre, António; Palma, Alberto; Pina, João Antonio; Pinto, Belmiro; Santos, Helena; Saraiva, João; Silva, José; Soares, Mara; Veloso, Filipe; Wolters, Helmut
    The top quark mass has been measured using the template method in the top antitop -> lepton + jets channel based on data recorded in 2011 with the ATLAS detector at the LHC. The data were taken at a proton-proton centre-of-mass energy of sqrt(s) = 7 TeV and correspond to an integrated luminosity of 1.04/fb. The analyses in the electron + jets and muon + jets decay channels yield consistent results. The top quark mass is measured to be m_top = 174.5 +/- 0.6_stat +/- 2.3_syst GeV.
    2012-06-21Journal article Open access Show more