The proton charge radius extracted from the Initial State Radiation experiment at MAMI

• Main Authors: Mihovilovič, Miha, Achenbach, Patrick, Beranek, Tobias, Beričič, Jure, Bernauer, Jan C, Böhm, Ralph, Bosnar, Damir, Cardinali, Matteo, Correa, Loup, Debenjak, Luka, Denig, Achim, Distler, Michael O, Esser, Anselm, Bondy, Maria I. Ferretti, Fonvieille, Helene, Friedrich, Jan M, Friščić, Ivica, Griffioen, Keith, Hoek, Matthias, Kegel, Simon, Kohl, Yvonne, Merkel, Harald, Middleton, Duncan G, Müller, Ulrich, Pochodzalla, Josef, Schlimme, Björn S, Schoth, Matthias, Schulz, Florian, Sfienti, Concettina, Širca, Simon, Štajner, Samo, Thiel, Michaela, Tyukin, Alexey, Vanderhaeghen, Marc, Weber, Adrian B
• Format: Journal Article
• Language: English
• Published: 27-05-2019
• Subjects: Physics - Nuclear Experiment
• DOI: 10.48550/arxiv.1905.11182

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 $(0.870 \pm 0.014_\mathrm{stat.}\pm 0.024_\mathrm{sys.}
\pm 0.003_\mathrm{mod.})\,\mathrm{fm}$.