We study the matching of multijet matrix elements and shower evolution in the
case of top production in hadronic collisions at the Tevatron and at the LHC.
We present the results of the matching algorithm implemented in the ALPGEN
Monte Carlo generator, and compare them with results obtained at the parton
level, and with the predictions of the MC@NLO approach. We highlight the
consistency of the matching algorithm when applied to these final states, and
the excellent agreement obtained with MC@NLO for most inclusive quantities. We
nevertheless identify also a remarkable difference in the rapidity spectrum of
the leading jet accompanying the top quark pair, and comment on the likely
origin of this discrepancy.Comment: 22 pages, 13 figures, 5 tables. JHEP styl