Hard-Pion Current Algebra, Unitarization, andI=0s-WaveππScattering

Abstract

Using current algebra and a method of pole and cut dominance, a two-parameter effective-range formula for the scalar $\pi \pi$ form factor is obtained. Our fit to the $I=0\mathrm{}$ $s$-wave $\pi \pi$ phase shift derived from this result favors the "up-down" solution and supports the existence of a broad $\epsilon$ resonance.