Positive helicity Einstein-Yang-Mills amplitudes from the double copy method

Abstract

All positive helicity four-point gluon-graviton amplitudes in Einstein-Yang-Mills theory coupled to a dilaton and axion field are computed at the leading one-loop order using color-kinematics duality. In particular, all relevant contributions in the gravitational and gauge coupling are established. This extends a previous generalized unitarity based computation beyond the leading terms in the gravitational coupling $\ensuremath{\kappa}$. The resulting purely rational expressions take very compact forms. The previously seen vanishing of the single-graviton-three-gluon amplitude at leading order in $\ensuremath{\kappa}$ is seen to be lifted at order ${\ensuremath{\kappa}}^{3}$.