Resonant Form Factors from Two-Body Transition Amplitudes

Due to the short lifetime of hadronic resonant states, constraining their structure has historically proven difficult; however, such information can be accessed through transition amplitudes that couple two-body states via an external current. Here I present an exact analytic representation for the on-shell form of these amplitudes in terms of generic form factors and known kinematic functions [Phys. Rev. D 103, 114512]. I will then show how it is possible to access the elastic form factors of resonances from this analytic representation. This framework combined with the finite-volume formalism presented in [Phys. Rev. D 100, 034511] constitutes a complete pipeline for extracting elastic resonant form factors from lattice QCD calculations.