Publication: Proton charge radius extraction from electron scattering data using dispersively improved chiral effective field theory
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2019-04-05
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APS Physics
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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 ≈ 0.5 GeV 2 and larger) and avoids the difficulties arising in methods relying on the Q 2 → 0 extrapolation. We obtain a radius of 0.844(7) fm, consistent with the high-precision muonic hydrogen results.