2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45411We discuss $ππ$ scattering in the framework of chiral perturbation theory. In particular, we recall the predictions made some time ago for the threshold parameters and for the phase shift difference $δ_0^0-δ_1^1$.6 pages, LaTex, uses epsf.tex and epsfig.sty; 2 uufiled figures included. To be published in the second edition of the DA$Φ$NE Physics Handbook, eds. L. Maiani, G. Pancheri and N. Paver (to appear)High Energy Physics - Phenomenologytext