Limits on the production of narrow t(t)over-bar resonances in p(p)over-bar collisions at root s=1.96 TeV

We search for evidence of resonant top quark pair production in 955 pb(-1) of p (p) over bar collisions at root s = 1: 96 TeV recorded with the CDF II detector at the Fermilab Tevatron. For fully reconstructed candidate t (t) over bar events triggered on leptons with large transverse momentum and containing at least one identified b-quark jet, we compare the invariant mass spectrum of t (t) over bar pairs to the expected superposition of standard model t (t) over bar, non-t (t) over bar backgrounds, and a simple resonance model based on a sequential Z' boson. We establish upper limits for sigma(p (p) over bar -> Z')center dot Br(Z' -> t (t) over bar) in the Z' mass interval from 450 GeV/c(2) to 900 GeV=c(2). A topcolor leptophobic Z' is ruled out below 720 GeV=c(2), and the cross section of any narrow Z'-like state decaying to t (t) over bar is found to be less than 0.64 pb at 95% C. L. for M(Z') above 700 GeV/c(2).