Abstract
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 m 2 π±- 2 πand free of any contributions from short-distance electromagnetic counterterms. The differential cross-section for charged pion Compton scattering π -γ→π -γ gets affected (in backward directions) at the level of a few permille only. At the same time the isospin-breaking correction leads to a small shift of the pion polarizability difference by δ(α π-β π)≃1. 3·10 -5 fm 3. In the case of the low-energy γγ→π 0π 0 reaction isospin breaking manifests itself through a cusp effect at the π +π - threshold. We give an improved estimate for this cusp effect using the empirical ππ-scattering length difference a0-a2\≃ 0.26πm -.
Original language | English |
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Article number | 1230009 |
Journal | International Journal of Modern Physics E |
Volume | 21 |
Issue number | 10 |
DOIs | |
State | Published - Oct 2012 |
Keywords
- Pion Compton scattering
- charged and neutral pion mass difference
- isospin-symmetry breaking correction
- pion electromagnetic polarizabilities
- pion-loop diagrams