Scattering amplitudes for QCD, gravity and massive particles

I will discuss basic on-shell approach to scattering amplitudes. As an example, I will outline the derivation of two infinite families of tree-level scattering amplitudes in QCD involving a massive quark pair. Then I will generalize one of them to gauge theory coupled to massive particles of general spin. This will allow me to discuss a novel chiral-field approach to massive higher-spin theory and applications to classical gravitational dynamics of rotating black holes.