MSc Defense: Marcos Skowronek Santos

Title: High Spin Scattering Amplitudes

Abstract: This thesis reviews and expands on the usage of scattering amplitude techniques to model gravitational collision events between rotating objects. In this formalism, classical angular momentum is encoded in an expansion in terms of the spin quantum number of the particles. By making use of the color-kinematics duality and the properties of Heavy-mass Effective Field Theories, we construct a fully covariant and spurious pole free form for the four- and five-point Compton amplitudes for a scattering process involving one massive spinning particle interacting with a number of massless gluons or gravitons. Using a bootstrap method where only gauge invariance and a correct factorization behavior are imposed, the solution is uniquely fixed when choosing a natural basis of functions to generate the ansatz. We also generalize this procedure to arbitrary number of particles. Lastly, we compare with several results in the literature and make appropriate contact term corrections to match the specific behavior for Kerr black hole collisions up to quartic order in spin.