Observed Properties of sigma-particle

TL;DR

This paper presents evidence for the sigma(600) meson through phase shift analysis and production processes, aligning its properties with the SU(2) linear sigma model and explaining background phase shifts via model interactions.

Contribution

It provides experimental evidence for the sigma meson and links its properties to the linear sigma model, including the role of background phase shifts and rho-meson contributions.

Findings

Evidence for sigma(600) from phase shift analysis

Sigma properties match SU(2) linear sigma model predictions

Background phase shift explained by lambda phi^4 interaction

Abstract

Recently we obtained the evidence for the existence of sigma(600) meson, which had been sought but missing for a long time, by reanalyzing the I=0 S-wave pi pi scattering phase shift. The sigma-existence was also suggested through the analyses of pi pi production processes, pp central collision pp to pp pi^0 pi^0 and J/psi to omega pi pi decay. The observed properties through these works of sigma meson satisfy the mass and width relation of SU(2) linear sigma model. The physical origin of the repulsive background phase shift delta_{BG}, which was essential to lead to the sigma-existence in our phase shift analysis, is also due to the "compensating lambda phi^4-interaction" in linear sigma model. Furthermore in this talk the experimental property of the delta_{BG} is shown to be describable quantitatively in the framework of linear sigma model including rho-meson contribution.