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Abstract

In this letter, we provide evidence for a new double-copy structure in one-loop amplitudes of the open superstring. Their integrands w.r.t. the moduli space of genus-one surfaces are cast into a form where gauge invariant kinematic factors and elliptic functions of the punctures enter on completely symmetric footing. In particular, replacing the elliptic functions by a second copy of kinematic factors maps one-loop open-string correlators to gravitational matrix elements of the higher-curvature operator $R^4$.