Cusp effects in meson decays
Helmholtz-Institut fūr Strahlen- und Kernphysik (Theorie) and
Bethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn,
a e-mail: email@example.com
Published online: 12 April 2010
The pion mass diﬀerence generates a pronounced cusp in the π0 π0 invariant mass distribution of K+ → π0 π0 π+ decays. As originally pointed out by Cabibbo, an accurate measurement of the cusp may allow one to pin down the S-wave pion–pion scattering lengths to high precision. We present the non-relativistic eﬀective ﬁeld theory framework that permits to determine the structure of this cusp in a straightforward manner, including the eﬀects of radiative corrections. Applications of the same formalism to other decay channels, in particular η and η′ decays, are also discussed.
© Owned by the authors, published by EDP Sciences, 2010