A search for resonant production of tt̄ pairs in 4.8 fb-1 of integrated luminosity of pp̄ collisions at √s=1.96 TeV

We search for resonant production of t (t) over bar pairs in 4.8 fb(-1) integrated luminosity of p (p) over bar collision data at root s = 1.96 TeV in the lepton + jets decay channel, where one top quark decays leptonically and the other hadronically. A matrix-element reconstruction technique is used; for each event a probability density function of the t (t) over bar candidate invariant mass is sampled. These probability density functions are used to construct a likelihood function, whereby the cross section for resonant t (t) over bar production is estimated, given a hypothetical resonance mass and width. The data indicate no evidence of resonant production of t (t) over bar pairs. A benchmark model of leptophobic Z' -> t (t) over bar is excluded with m(Z') < 900 GeV/c(2) at 95% confidence level.