https://doi.org/10.1140/epja/i2016-16331-7
Regular Article - Theoretical Physics
On the 
continuum in the nucleon form factors and the proton radius puzzle
1
Institute for Nuclear Theory, University of Washington, 98195-1550, Seattle, WA, USA
2
Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, D-53115, Bonn, Germany
3
Institut für Kernphysik, Technische Universität Darmstadt, D-64289, Darmstadt, Germany
4
ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291, Darmstadt, Germany
5
Institut für Kernphysik, Institute for Advanced Simulation, and Jülich Center for Hadron Physics, Forschungszentrum Jülich, D-52425, Jülich, Germany
* e-mail: mhofer@uw.edu
Received:
22
September
2016
Accepted:
21
October
2016
Published online:
16
November
2016
We present an improved determination of the continuum contribution to the isovector spectral functions of the nucleon electromagnetic form factors. Our analysis includes the most up-to-date results for the 
partial waves extracted from Roy-Steiner equations, consistent input for the pion vector form factor, and a thorough discussion of isospin-violating effects and uncertainty estimates. As an application, we consider the contribution to the isovector electric and magnetic radii by means of sum rules, which, in combination with the accurately known neutron electric radius, are found to slightly prefer a small proton charge radius.
© SIF, Springer-Verlag Berlin Heidelberg, 2016
