  We study contributions of a scalar diquark particle in a color representation
of anti-triplet and sextet to the top quark pair production at the Tevatron and
the Large hadron collider (LHC). The model can give Forward-Backward (FB)
asymmetry at the Tevatron while can avoid the same sign top quark production at
the LHC by assuming the top-number conserving diquark couplings. We study
compatibility between the large positive FB asymmetry observed at the Tevatron
and non-observation of the charge asymmetry at the LHC, by including
contributions from the single and pair production of diquarks. We find that the
whole parameter space of the models can soon be explored at the LHC by
measuring the total t-tbar production cross section and the inclusive charge
asymmetry with smaller uncertainties. In addition, we compare the statistical
significance of the charge asymmetry measured at the LHC with that of the
optimal observable of the subprocess FB asymmetry, and find that they are
comparable even when we ignore the uncertainty in the parton distribution
functions.
