Revisiting collisional Penrose processes in terms of escape probabilities for spinning particles.

We first study the escape probability of a spinning particle emitted from a Kerr black hole and find that the escape probability increases with the spin of the particle around the extreme Kerr black hole; in contrast, the escape probability decreases at the position near the horizon but increases at the position far from the horizon with the increasing spin of the particle. We then probe the relation between the escape probabilities and the energy extraction efficiencies of collisional Penrose processes for particles with varying spin. For an extreme Kerr black hole, the efficiency increases with the escape probability; for a nonextreme Kerr black hole, the near-horizon efficiency decreases with the escape probability, while the efficiency may increase with the escape probability in the ergosphere. In the event horizon limit, we also find that the average escape probability of the spinning particle produced in the collisional Penrose process decreases with the rotation parameter of the Kerr black hole. [ABSTRACT FROM AUTHOR]