$K \to \pi\pi$ phenomenology in the presence of electromagnetism

V. Cirigliano; J.F. Donoghue; E. Golowich

doi:doi:10.1007/s100520000530

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2024 Impact factor 4.8

Particles and Fields

Eur. Phys. J. C 18, 83-95
DOI 10.1007/s100520000530

$K \to \pi\pi$ phenomenology in the presence of electromagnetism

V. Cirigliano - J.F. Donoghue - E. Golowich

Department of Physics and Astronomy, University of Massachusetts, Amherst, MA 01003, USA

Received: 28 August 2000 / Published online: 13 November 2000 - © Springer-Verlag 2000

Abstract
We describe the influence of electromagnetism on the phenomenology of $K \to \pi\pi$ decays. This is required because the present data were analyzed without inclusion of electromagnetic radiative corrections, and hence contain several ambiguities and uncertainties which we describe in detail. Our presentation includes a full description of the infrared effects needed for a new experimental analysis. It also describes the general treatment of final state interaction phases, needed because Watson's theorem is no longer valid in the presence of electromagnetism. The phase of the isospin-two amplitude ${\cal A}_2$ may be modified by $50 \to 100\%$ . We provide a tentative analysis using present data in order to illustrate the sensitivity to electromagnetic effects, and also discuss how the standard treatment of $\epsilon' /\epsilon$ is modified.