## Abstract

We develop a general formalism for computing classical observables for relativistic scattering of spinning particles, directly from on-shell amplitudes. We then apply this formalism to minimally coupled Einstein-gravity amplitudes for the scattering of massive spin 1/2 and spin 1 particles with a massive scalar, constructed using the double copy. In doing so we reproduce recent results at first post-Minkowskian order for the scattering of spinning black holes, through quadrupolar order in the spin-multipole expansion.

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Maybee, B., Oâ€™Connell, D. & Vines, J. Observables and amplitudes for spinning particles and black holes.
*J. High Energ. Phys.* **2019**, 156 (2019). https://doi.org/10.1007/JHEP12(2019)156

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DOI: https://doi.org/10.1007/JHEP12(2019)156

### Keywords

- Scattering Amplitudes
- Black Holes