  We numerically investigate the formation of D-dimensional black holes in
high-energy particle collision with the impact parameter and evaluate the total
cross section of the black hole production. We find that the formation of an
apparent horizon occurs when the distance between the colliding particles is
less than 1.5 times the effective gravitational radius of each particles. Our
numerical result indicates that although both the one-dimensional hoop and the
(D-3)-dimensional volume corresponding to the typical scale of the system give
a fairly good condition for the horizon formation in the higher-dimensional
gravity, the (D-3)-dimensional volume provide a better condition to judge the
existence of the horizon.
