Proton charge radius extraction from electron scattering data using dispersively improved chiral effective field theory

Alarcón, J.M. (Departamento de Física Teórica, Universidad Complutense de Madrid, 28040 Madrid, Spain) ; Higinbotham, D.W. (Jefferson Lab, Newport News, Virginia 23606, USA) ; Weiss, C. (Jefferson Lab, Newport News, Virginia 23606, USA) ; Ye, Zhihong (Argonne National Laboratory, Argonne, Illinois 60439, USA)

09 April 2019

Abstract: We extract the proton charge radius from the elastic form factor (FF) data using a novel theoretical framework combining chiral effective field theory and dispersion analysis. Complex analyticity in the momentum transfer correlates the behavior of the spacelike FF at finite ${Q}^{2}$ with the derivative at ${Q}^{2}=0$. The FF calculated in the predictive theory contains the radius as a free parameter. We determine its value by comparing the predictions with a descriptive global fit of the spacelike FF data, taking into account the theoretical and experimental uncertainties. Our method allows us to use the finite-${Q}^{2}$ FF data for constraining the radius (up to ${Q}^{2}\approx 0.5{\mathrm{GeV}}^{2}$ and larger) and avoids the difficulties arising in methods relying on the ${Q}^{2}\to 0$ extrapolation. We obtain a radius of 0.844(7) fm, consistent with the high-precision muonic hydrogen results.

Published in: Physical Review C 99 (2019)