Light σ-Meson Production in Excited Υ Decay Processes II : Theoretical Investigation(§3. ππ Production Processes,Possible Existence of the σ-Meson and Its Implications to Hadron Physics)

Abstract

The results of analyses obtained in Part I are examined from the viewpoint of chiral symmetry. The mass spectra of ππ system are widely believed to be suppressed generally near the threshold, because of the derivative coupling property of Nambu-Goldstone π meson. However, this suppression does not hold in the processes with large energy release, and the steep increase from the ππ threshold observed in the transition Υ(3S → 1S) is shown to be consistent with general constraints from chiral symmetry.