New signals in pair production of heavy Q=2/3 singlets at LHC
  New quark singlets T can be produced in pairs at LHC through standard QCD interactions, with a large cross section for masses of several hundreds of GeV. Their charged current decays T Tbar T -> W+ b W- bbar, with semileptonic decay of the W pair, give a final state l nu bb jj$, as in top pair production. The mixed decay modes T Tbar -> W+ b H tbar, H t W- bbar -> W+ b W- bbar H, T Tbar -> W+ b Z tbar, Z t W- bbar -> W+ b W- bbar Z, with H,Z -> jj, yield two more jets, l nu bb jjjj, or the same state in the latter case for Z -> nu nubar. We extend previous work examining in detail the extra H and Z contributions and stressing one of the salient features of the T Tbar -> W+ b W- bbar signal: the presence of a very energetic charged lepton. We finally compare with the discovery potential in l nu bbbb jj final states, with four b tags. 
J. A. Aguilar-Saavedra