# Positive helicity Einstein-Yang-Mills amplitudes from the Double Copy

## TL;DR

This paper computes one-loop positive helicity four-point amplitudes involving gluons and gravitons in Einstein-Yang-Mills theory, revealing new rational expressions and the lifting of certain amplitude vanishing conditions.

## Contribution

It extends previous unitarity-based calculations to include higher-order gravitational couplings using colour-kinematics duality.

## Key findings

- Explicit one-loop amplitudes are derived in compact rational form.
- The vanishing of the single-graviton-three-gluon amplitude at leading order is lifted at order κ^3.
- The calculations incorporate contributions from dilaton and axion fields.

## 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 colour-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 $\kappa$. The resulting purely rational expressions take very compact forms. The previously seen vanishing of the single-graviton-three-gluon amplitude at leading order in $\kappa$ is seen to be lifted at order $\kappa^{3}$.