Roper resonance $N^*(1440)$ from charmonium decays

Abstract

The Roper resonance $N^*(1440)$ was discovered by David Roper in 1964 through sophisticated partial-wave analyses of $\pi N$ scattering data. However the first direct observation of the Roper resonance peak in the $\pi N$ invariant mass spectrum was only realized 40 years later from the charmonium decay $J/\psi\to\bar pn\pi^+ +c.c.$ at Beijing Electron-Positron Collider. The further observations of the Roper resonance production from various charmonium decays helped to reveal its multiquark nature with large $\sigma N$ component.