  This work considers a variation of the massive ambitwistor string model
presented in arXiv:2301.11227 that describes supergravity and super-Yang-Mills
on the Coulomb branch simultaneously with a single Lagrangian. All-multiplicity
tree and one-loop amplitudes are evaluated and shown to have proper unitary
factorization. The massless limit provides Einstein Yang-Mills Amplitudes
including multiple gluon traces. It is argued that the cosmological constant
vanishes at all orders of perturbation theory. As application results for
Compton scattering are obtained and compared with ones in the literature.
