If there is a Z' with typical electroweak scale couplings to the ordinary fermions, it should be readily observable at the LHC for masses up to ~ 4 - 5 TeV, or at the Tevatron for masses up to ~ 600 - 900 GeV. Significant diagnostic probes of the Z' couplings would be possible up to 2 - 2.5 TeV. The latest results from CDF with 955 pb^-1 data ruled out topcolor leptophobic Z' below 720 GeV/c^2, and the cross section of Z'-like state decaying to ttbar is found to be less than 0.64 pb at 95% C.L. for M_Z' above 700 GeV/c^2 (Ref: T. Aaltonen et.al., PRD 77, 051102(R) (2008)).
With the increase of Z' mass and significantly high CM Energy at LHC (14 TeV proton-proton head on collision), the Top pairs from Z' decay will be highly boosted. It's a big challenge to reconstruct Top using b jet and W hadronic decay products (-> 2 jets) since they are largely overlapped. Apparently, large jet cone size (e.g. default value R = 0.7) is not suitable for Z' study simply because most of jets from highly boosted top decay are located in a relative small region. It is crucial to find suitable calorimeter clustering algorithms and jet finding algorithms to efficiently separate these hadronic jets and to well reconstruct W and Top. Our studies about performances of eight available jet algorithms are available ( Ref: ATLAS Jet Performance ), the Kt4Jets algorithm yields the best results for Z'->ttbar study based on the reconstruction performance(efficiency, mass and mass resolution etc.) of W and Top.
