Arguments on the Light-mass Scalar Mesons and Concluding Remarks of the Meson Sessions

Abstract

This report attempts to summarize the most interesting (and hopefully important) results leading up to and including those presented at the recent Symposium sponsored jointly by the Institute of Quantum Science at Nihon University and KEK. My task is to present the arguments on light-mass scalar mesons below 1 GeV from both theory and phenomenological viewpoints, including the new insight gained on $π-π$ production and scattering amplitudes. Specific topics are taken up, particularly on the existence of a $σ$(500-600) as explanation of the twin peak anomaly in $Υ(3S) \to Υ(1S)ππ$, the status of $J^{PC}=1^{-+}$ states and a possible crypto-exotic hybrid with $J^{PC}=0^{-+}$ are discussed, as well as the intriguing enhancement in $p\bar{p}$ radiative decay from $J/ψ$.