  We present new formulas for one-loop ambitwistor-string correlators for gauge
theories in any even dimension with arbitrary combinations of gauge bosons,
fermions and scalars running in the loop. Our results are driven by new
all-multiplicity expressions for tree-level two-fermion correlators in the RNS
formalism that closely resemble the purely bosonic ones. After taking forward
limits of tree-level correlators with an additional pair of fermions/bosons,
one-loop correlators become combinations of Lorentz traces in vector and spinor
representations. Identities between these two types of traces manifest all
supersymmetry cancellations and the power counting of loop momentum. We also
obtain parity-odd contributions from forward limits with chiral fermions.
One-loop numerators satisfying the Bern-Carrasco-Johansson (BCJ) duality for
diagrams with linearized propagators can be extracted from such correlators
using the well-established tree-level techniques in Yang-Mills theory coupled
to biadjoint scalars. Finally, we obtain streamlined expressions for BCJ
numerators up to seven points using multiparticle fields.
