# Maximal Efficiency of Collisional Penrose Process with Spinning Particle II

## TL;DR

This paper investigates the maximum energy extraction efficiency of the collisional Penrose process near an extremal Kerr black hole, considering both spinning and non-spinning particles, and finds significant efficiency enhancements with particle spin.

## Contribution

It provides detailed calculations of maximal efficiency for collisional Penrose processes involving spinning particles, extending previous analyses to include particle spin effects.

## Key findings

- Maximum efficiency ~2.56 for elastic collision with non-spinning particles
- Maximum efficiency ~7 for photoemission with non-spinning particles
- Maximum efficiency ~8.44 for elastic collision with spinning particles

## Abstract

We analyze the collisional Penrose process between a particle on the ISCO orbit around an extreme Kerr black hole and a particle impinging from infinity. We consider both cases with non-spinning and spinning particles. We evaluate the maximal efficiency, $\eta_{\text{max}}=(\text{extracted energy})/(\text{input energy})$, for the elastic collision of two massive particles and for the photoemission process, in which the ISCO particle will escape to infinity after the collision with a massless impinging particle. For non-spinning particles, the maximum efficiency is $\eta_{\text{max}} \approx 2.562$ for the elastic collision and $\eta_{\text{max}} \approx 7$ for the photoemission process. While for spinning particles we obtain the maximal efficiency $\eta_{\text{max}} \approx 8.442$ for the elastic collision and $\eta_{\text{max}} \approx 12.54$ for the photoemission process.