Khuri–Treiman equations for $\pi$$\pi$ scattering

Abstract

The Khuri–Treiman formalism models the partial-wave expansion of a scattering amplitude as a sum of three individual truncated series, capturing the low-energy dynamics of the direct and cross channels. We cast this formalism into dispersive equations to study $\pi$$\pi$ scattering, and compare their expressions and numerical output to the Roy and GKPY equations. We prove that the Khuri–Treiman equations and Roy equations coincide when both are truncated to include only S- and P-waves. When higher partial waves are included, we find an excellent agreement between the Khuri–Treiman and the GKPY results. This lends credence to the notion that the Khuri–Treiman formalism is a reliable low-energy tool for studying hadronic reaction amplitudes.