ar X iv : h ep - p h / 00 05 10 6 v 3 2 2 M ay 2 00 2 Footprints of a Broad σ ( 600 ) in Weak - Interaction Processes

We explore how chiral-symmetry constraints on weak-interaction matrix elements point toward the existence of an intermediate-state σ in several different weak-interaction processes. Particular attention is directed toward recent evidence for a σ within three-body nonleptonic weak decays. PACS numbers: 11.30.Rd, 11.40.Ha, 14.40.Cs HIP-2000-22/TH The existence of a broad scalar-isoscalar ππ resonance near 600 MeV has long been controversial. After having been absent for many years from the listings of the Particle Data Group (PDG) in the Reviews of Particle Physics [1], this resonance has reappeared under the name “f0(400− 1200) or σ” (hereafter called σ(600)) after reanalysis by several groups [2] of the available data on the scalar nonet and ππ phase shifts. Today an increasing number of theoretical and experimental analyses point toward the existence of this important meson