https://doi.org/10.1140/epja/s10050-021-00414-x
Regular Article – Experimental Physics
The proton charge radius extracted from the initial-state radiation experiment at MAMI
1
Faculty of Mathematics and Physics, University of Ljubljana, 1000, Ljubljana, Slovenia
2
Jožef Stefan Institute, 1000, Ljubljana, Slovenia
3
Institut für Kernphysik, Johannes-Gutenberg-Universität Mainz, 55128, Mainz, Germany
4
Massachusetts Institute of Technology, 02139, Cambridge, MA, USA
5
Department of Physics, Faculty of Science, University of Zagreb, 10002, Zagreb, Croatia
6
Université Clermont Auvergne, CNRS/IN2P3, LPC, BP 10448, 63000, Clermont-Ferrand, France
7
Physik Department, Technische Universität München, 85748, Garching, Germany
Received:
2
November
2020
Accepted:
4
March
2021
Published online:
29
March
2021
We report on a comprehensive reinterpretation of the existing cross-section data for elastic electron-proton scattering obtained by the initial-state radiation technique, resulting in a significantly improved accuracy of the extracted proton charge radius. By refining the external energy corrections we have achieved an outstanding description of the radiative tail, essential for a detailed investigation of the proton finite-size effects on the measured cross sections. This development, together with a novel framework for determining the radius, based on a regression analysis of the cross sections employing a polynomial model for the form factor, led us to a new value for the charge radius, which is 
Key words: Initial-state radiation / Proton radius / Radiative corrections
© The Author(s) 2021
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