Maximal efficiency of the collisional Penrose process with spinning particles

We analyze the collisional Penrose process of spinning test particles in an extreme Kerr black hole. We consider that two particles plunge into the black hole from infinity and collide near the black hole. For the collision of two massive particles, if the spins of particles are s1≈0.01379 μM and s2≈-0.2709 μM, we obtain the maximal efficiency is about ηmax=(extracted energy)/(input energy)≈15.01, which is more than twice as large as the case of the collision of non-spinning particles (ηmax≈6.32). We also evaluate the collision of a massless particle without spin and a massive particle with spin (Compton scattering), in which we find the maximal efficiency is ηmax≈26.85 when s2≈-0.2709 μM, which should be compared with ηmax≈13.93 for the nonspinning case.