ATLAS collaboration (3040 authors)Aguilar-Saavedra, Juan AntonioAmaral, PedroAnjos, NunoCarvalho, JoãoCastro, Nuno FilipeConde Muiño, PatriciaDo Valle Wemans, AndréFiolhais, MiguelGomes, AgostinhoGonçalo, RicardoJorge, PedroLopes, LourencoMachado Miguens, JoanaMaio, AméliaManeira, JoséOliveira, Miguel AlfonsoOnofre, AntónioPalma, AlbertoPina, João AntonioPinto, BelmiroSantos, HelenaSaraiva, JoãoSilva, JoséSoares, MaraVeloso, FilipeWolters, Helmut2019-02-032019-02-032012-02http://dx.doi.org/10.1103/PhysRevLett.109.032001http://hdl.handle.net/10400.26/26115This Letter presents a search for pair production of heavy down-type quarks decaying via b'->Wt in the lepton + jets channel, as b'b'->WtWt->bbWWWW->lvbbqqqqqq. In addition to requiring exactly one lepton, large missing transverse momentum and at least six jets, the invariant mass of nearby jet pairs is used to identify high transverse momentum W bosons. In data corresponding to an integrated luminosity of 1.04 fb^-1 from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector, a heavy down-type quark with mass less than 480 GeV is excluded at the 95% confidence level.engjournal article2019-02-03