Phase Motion in the Scalar Low-Mass $\pi^-\pi^+$ Amplitude in $D^+ \to \pi^-\pi^+\pi^+$

TL;DR

This paper presents a direct, model-independent measurement of the low-mass $^+^-$ phase motion in $D^+ o ^-^+^+$ decay, confirming the existence of the $(500)$ scalar meson.

Contribution

It provides the first direct, model-independent measurement of the $^+^-$ phase motion in this decay, confirming the $(500)$ meson evidence.

Findings

Strong phase variation observed, compatible with $(500)$ meson.

Results confirm previous Fermilab E791 findings.

Supports the existence of the scalar $(500)$ meson.

Abstract

This work is a direct and model-independent measurement of the low mass $\pi^+\pi^-$ phase motion in the $D^+ \to \pi^-\pi^+\pi^+$ decay. The results show a strong phase variation, compatible with an isoscalar $\sigma(500)$ meson. This result confirms the previous Fermilab E791 result which found evidence for the existence of this scalar particle using a full Dalitz-plot analysis.