  An analysis of the spin correlation effects in top quark pair production at
hadron colliders is presented with special emphasis for the Large Hadron
Collider (LHC). At the LHC top quark pair production is dominated by
gluon-gluon fusion. For gluon-gluon fusion at high energies the production is
dominated by unlike helicity gluon fusion which has the same spin correlations
as quark-antiquark annihilation. At low energies the production is dominated by
like helicity gluon fusion which imparts very strong azimuthal correlations on
the di-lepton decay products in top quark pair decay. This production process
is studied in detail and this suggest a new way to look for spin correlations
in top quark pair production at the LHC.
