  The center-of-mass energy of two colliding particles could be arbitrarily
high in the vicinity of event horizons of the extremal Myers-Perry black holes
if the angular momentum of colliding particles is fine-tuned to the critical
values. We investigate the maximum efficiency of two colliding particles in
four and six dimensions. The efficiency of collision for two particles near the
four-dimensional Kerr black holes is 130 %. We show that the efficiency
increases to 145 % for collision in six dimensions. We also show that the
region for the polar angle in which the particle can reach the high energy is
larger when the dimension of space-time increases.
