Abstract : We search for resonant production of tt¯ pairs in 4.8fb-1 integrated luminosity of pp¯ collision data at s=1.96TeV 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 tt¯ candidate invariant mass is sampled. These probability density functions are used to construct a likelihood function, whereby the cross section for resonant tt¯ production is estimated, given a hypothetical resonance mass and width. The data indicate no evidence of resonant production of tt¯ pairs. A benchmark model of leptophobic Z'→tt¯ is excluded with mZ'<900GeV/c2 at 95% confidence level.