High energy particle collisions near black holes

If two geodesic particles collide near a rotating black hole, their energy in the centre of mass frame E-c.m. can become unbound under certain conditions (the so-called BSW effect). The special role is played here by so-called critical geodesics when one of particles has fine-tuned energy and angular momentum. The nature of geodesics reveals itself also in fate of the debris after collisions. One of particles moving to a remote observer is necessarily near-critical. We discuss, when such a collision can give rise not only unboud E-c.m. but also unbound Killing energy E (so-called super-Penrose process).