Double Copy of Form Factors and Higgs Amplitudes: A Mechanism for Turning Spurious Poles in Yang-Mills Theory into Physical Poles in Gravity

Abstract

We extend the double-copy picture of scattering amplitudes to a class of matrix elements (so-called form factors) that involve local gauge-invariant operators. Both the Bern, Carrasco, and Johansson (BCJ) and the Kawai, Lewellen, and Tye formalisms are considered and novel properties are observed. One remarkable feature is that through the double-copy construction, certain spurious poles hidden in the gauge form factors become physical propagators in gravity. This mechanism also reveals new hidden relations for form factors which can be understood as a generalization of the BCJ relations.