https://doi.org/10.1140/epjc/s10052-021-09661-0
Regular Article - Theoretical Physics
Towards an improved understanding of 
1
Helmholtz-Institut für Strahlen- und Kernphysik (Theorie), Universität Bonn, 53115, Bonn, Germany
2
Bethe Center for Theoretical Physics, Universität Bonn, 53115, Bonn, Germany
3
Instituto de Física Corpuscular, Universitat de València–Consejo Superior de Investigaciones Científicas, Parc Científic, 46980, Paterna, Valencia, Spain
4
Institut für Kernphysik (Theorie), Institute for Advanced Simulation, and Jülich Center for Hadron Physics, Forschungszentrum Jülich, 52425, Jülich, Germany
5
School of Physics and Electronics, Central South University, 410083, Changsha, China
6
Tbilisi State University, 0186, Tbilisi, Georgia
Received:
9
June
2021
Accepted:
16
September
2021
Published online:
13
November
2021
We argue that high-quality data on the reaction 
will allow one to determine the doubly-virtual form factor 
in a model-independent way with controlled accuracy. This is an important step towards a reliable evaluation of the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. When analyzing the existing data for for total energies squared 
, we demonstrate that the effect of the 
meson provides a natural breaking mechanism for the commonly employed factorization ansatz in the doubly-virtual form factor 
. However, better data are needed to draw firm conclusions.
© The Author(s) 2021
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