  We generalize the scattering equations to include both massless and massive
particles. We construct an expression for the tree-level n-point amplitude with
n-2 gluons or gravitons and a pair of massive scalars in arbitrary spacetime
dimension as a sum over the (n-3)! solutions of the scattering equations, a la
Cachazo, He, and Yuan. We derive the BCJ relations obeyed by these massive
amplitudes.
