Novel evaluation of the two-pion contribution to the nucleon isovector form factors

Abstract

We calculate the two-pion continuum contribution to the nucleon isovector spectral functions drawing upon the new high statistics measurements of the pion form factor by the CMD-2, KLOE, and SND collaborations. The general structure of the spectral functions remains unchanged, but the magnitude increases by about 10%. Using the updated spectral functions, we calculate the contribution of the two-pion continuum to the nucleon isovector form factors and radii. We compare the isovector radii with simple rho-pole models and illustrate their strong underestimation in such approaches. Moreover, we give a convenient parametrization of the result for use in future form factor analyses.

arXiv comment9 pages, 2 eps figures, revtex4, CMD-2 and SND data included, conclusions unchanged, version to appear in Phys. Lett. B

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