caa a22 4500 445873159 CHVBK 20180317145518.0 cr unu---uuuuu 170323e20110201xx s 000 0 eng 10.1140/epja/i2011-11015-6 doi (NATIONALLICENCE)springer-10.1140/epja/i2011-11015-6 Kaiser N. Physik-Department, Technische Universität München, D-85747, Garching, Germany aut Isospin breaking in pion Compton scattering [Elektronische Daten] [N. Kaiser] 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 $\ensuremath{m_{\pi^\pm}^2-m_{\pi^0}^2}$ and free of (electromagnetic) counterterm contributions. The differential cross-section for charged pion Compton scattering $\ensuremath{\pi^-\gamma \rightarrow \pi^-\gamma}$ 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 $\ensuremath{\delta(\alpha_\pi- \beta_\pi) \simeq 1.3 \cdot 10^{-5}}$ fm^3. In case of the low-energy $\ensuremath{\gamma\gamma \rightarrow \pi^0\pi^0}$ reaction isospin breaking manifests itself through a cusp effect at the $\ensuremath{\pi^+\pi^-}$ threshold. We give an improved estimate for it based on the empirical $ \pi$ $ \pi$ -scattering length difference $\ensuremath{a_0-a_2}$ . The Author(s), 2011 The European Physical Journal A Springer-Verlag 47/2(2011-02-01), 1-4 1434-6001 47:2<1 2011 47 10050 https://doi.org/10.1140/epja/i2011-11015-6 text/html Onlinezugriff via DOI 1 review-article jats NATIONALLICENCE 856 40 https://doi.org/10.1140/epja/i2011-11015-6 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Kaiser N. Physik-Department, Technische Universität München, D-85747, Garching, Germany aut NATIONALLICENCE 773 0- The European Physical Journal A Springer-Verlag 47/2(2011-02-01), 1-4 1434-6001 47:2<1 2011 47 10050 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer