The size of the proton - closing in on the radius puzzle

Abstract

We analyze the recent electron-proton scattering data from Mainz using a dispersive framework that respects the constraints from analyticity and unitarity on the nucleon structure. We also perform a continued fraction analysis of these data. We find a small electric proton charge radius, r_E^p = 0.84_{-0.01}^{+0.01} fm, consistent with the recent determination from muonic hydrogen measurements and earlier dispersive analyses. We also extract the proton magnetic radius, r_M^p = 0.86_{-0.03}^{+0.02} fm, consistent with earlier determinations based on dispersion relations.

4 pages, 2 figures, fit improved, small modifications, section on continued fractions modified, conclusions on the proton charge radius unchanged, version accepted for publication in European Physical Journal A

References in corpus (9)

• High-precision determination of the electric and magnetic form factors of the proton
• Dispersion analysis of the nucleon form factors including meson continua
• Measurement of sigma(e+ e- -> pi+ pi-) from threshold to 0.85 GeV^2 using Initial State Radiation with the KLOE detector
• Model independent extraction of the proton charge radius from electron scattering
• Measurements of the Electric Form Factor of the Neutron up to Q2=3.4 GeV2 using the Reaction He3(e,e'n)pp
• Roy-Steiner equations for pion-nucleon scattering
• Model independent extraction of the proton magnetic radius from electron scattering
• Updated dispersion-theoretical analysis of the nucleon electromagnetic form factors
• Model-independent extraction of two-photon effects in elastic electron-proton scattering

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