Date of this Version
Physical Review Letters 107, 082001 (2011); DOI: 10.1103/PhysRevLett.107.082001
We present a search for pair production of a fourth generation tl quark and its antiparticle, followed by their decays to a W boson and a jet, based on an integrated luminosity of 5.3 fb-1 of proton-antiproton collisions at √s= 1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the tlt-l production cross section that exclude at the 95% C.L. a tl quark that decays exclusively to W + jet with a mass below 285 GeV. We observe a small excess in the µ + jets channel which reduces the mass range excluded compared to the expected limit of 320 GeV in the absence of a signal.