Cusps in K --> 3 pi decays
arXiv:hep-ph/0604084 · doi:10.1016/j.physletb.2006.05.017
Abstract
The pion mass difference generates a pronounced cusp in K --> 3 pi decays. As has recently been pointed out by Cabibbo and Isidori, an accurate measurement of the cusp may allow one to pin down the S-wave pi pi scattering lengths to high precision. Here, we present and illustrate an effective field theory framework that allows one to determine the structure of this cusp in a straightforward manner. The strictures imposed by analyticity and unitarity are respected automatically.
14 pages, 3 figures, uses Elsevier style