Isospin breaking in pion Compton scattering
Physik-Department, Technische Universität München, D-85747, Garching, Germany
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Accepted: 5 January 2011
Published online: 1 February 2011
Using chiral perturbation theory we calculate for pion Compton scattering the isospin-breaking effects induced by the difference between the charged and neutral pion mass. At one-loop order this correction is directly proportional to and free of (electromagnetic) counterterm contributions. The differential cross-section for charged pion Compton scattering gets affected (in backward directions) at the level of a few permille. At the same time the isospin-breaking correction leads to a small shift of the pion polarizabilities by fm^3. In case of the low-energy reaction isospin breaking manifests itself through a cusp effect at the threshold. We give an improved estimate for it based on the empirical -scattering length difference .
© SIF, Springer-Verlag Berlin Heidelberg, 2011