Cross Section, Final Spin, and Zoom-Whirl Behavior in High-Energy Black-Hole Collisions

We study the collision of two highly boosted equal-mass, nonrotating black holes with generic impact parameter. We find such systems to exhibit zoom-whirl behavior when fine-tuning the impact parameter. Near the threshold of immediate merger the remnant black-hole Kerr parameter can be near maximal (a/M greater than or similar to 0: 95) and the radiated energy can be as large as 35 +/- 5% of the center-of-mass energy.