Scattering angles in Kerr metrics

Scattering angles for probes in Kerr metrics are derived for scattering in the equatorial plane of the black hole. We use a method that naturally resums all orders in the spin of the Kerr black hole, thus facilitating comparisons with scattering-angle computations based on the post-Minkowskian expansion from scattering amplitudes or worldline calculations. We extend these results to spinning black-hole probes up to and including second order in the probe spin and any order in the post-Minkowskian expansion for probe spins aligned with the Kerr spin. When truncating to third post-Minkowskian order, our results agree with those obtained by amplitude and worldline methods.