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Corrections to Sirlin's Theorem in $O(p^6)$ Chiral Perturbation Theory

P. Post·K. Schilcher
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Abstract

We present the results of the first two-loop calculation of a form factor in full $SU(3) \times SU(3)$ Chiral Perturbation Theory. We choose a specific linear combination of $π^+, K^+, K^0$ and $Kπ$ form factors (the one appearing in Sirlin's theorem) which does not get contributions from order $p^6$ operators with unknown constants. For the charge radii, the correction to the previous one-loop result turns out to be significant, but still there is no agreement with the present data due to large experimental uncertainties in the kaon charge radii.

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P. Post, K. Schilcher. 1997-01-30. Corrections to Sirlin's Theorem in $O(p^6)$ Chiral Perturbation Theory. https://doi.org/10.1103/physrevlett.79.4088

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