Proton Charge Radius from Electron Scattering
Department of Physics, University of Basel, Basel CH4056, Switzerland
Received: 21 November 2017 / Revised: 19 December 2017 / Accepted: 20 December 2017 / Published: 30 December 2017
The rms-radius R
of the proton charge distribution is a fundamental quantity needed for precision physics. This radius, traditionally determined from elastic electron-proton scattering via the slope of the Sachs form factor
extrapolated to momentum transfer
, shows a large scatter. We discuss the approaches used to analyze the e-p data, partly redo these analyses in order to identify the sources of the discrepancies and explore alternative parameterizations. The problem lies in the model dependence of the parameterized
needed for the extrapolation. This shape of
is closely related to the shape of the charge density
at large radii r
, a quantity that is ignored in most analyses. When using our physics knowledge about this large-r
density together with the information contained in the high-q
data, the model dependence of the extrapolation is reduced, and different parameterizations of the pre-2010 data yield a consistent value for
fm. This value disagrees with the more precise value
fm determined from the Lamb shift in muonic hydrogen.
This is an open access article distributed under the Creative Commons Attribution License
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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MDPI and ACS Style
Sick, I. Proton Charge Radius from Electron Scattering. Atoms 2018, 6, 2.
Sick I. Proton Charge Radius from Electron Scattering. Atoms. 2018; 6(1):2.
Sick, Ingo. 2018. "Proton Charge Radius from Electron Scattering." Atoms 6, no. 1: 2.
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