The proton charge radius extracted from the initial-state radiation experiment at MAMI
M. Mihovilovič, P. Achenbach, T. Beranek, J. Beričič, J. C. Bernauer, R. Böhm, D. Bosnar, M. Cardinali, L. Correa, L. Debenjak, A. Denig, M. O. Distler, A. Esser, M. I. Ferretti Bondy, H. Fonvieille, J. M. Friedrich, I. Friščić, M. Hoek, S. Kegel, H. Merkel, D. G. Middleton, U. Müller, J. Pochodzalla, B. S. Schlimme, M. Schoth, F. Schulz, C. Sfienti, S. Širca, S. Štajner, Y. Stöttinger, M. Thiel, A. Tyukin, Marc Vanderhaeghen, A. B. Weber
Abstract
Abstract 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 $$(0.878 \pm 0.011_\mathrm {stat.}\pm 0.031_\mathrm {sys.}\pm 0.002_\mathrm {mod.})\,\mathrm {fm}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>0.878</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0</mml:mn> <mml:mo>.</mml:mo> <mml:msub> <mml:mn>011</mml:mn> <mml:mrow> <mml:mi>stat</mml:mi> <mml:mo>.</mml:mo> </mml:mrow> </mml:msub> <mml:mo>±</mml:mo> <mml:mn>0</mml:mn> <mml:mo>.</mml:mo> <mml:msub> <mml:mn>031</mml:mn> <mml:mrow> <mml:mi>sys</mml:mi> <mml:mo>.</mml:mo> </mml:mrow> </mml:msub> <mml:mo>±</mml:mo> <mml:mn>0</mml:mn> <mml:mo>.</mml:mo> <mml:msub> <mml:mn>002</mml:mn> <mml:mrow> <mml:mi>mod</mml:mi> <mml:mo>.</mml:mo> </mml:mrow> </mml:msub> <mml:mo>)</mml:mo> <mml:mspace/> <mml:mi>fm</mml:mi> </mml:mrow> </mml:math>