The π→ππ process in nuclei and the restoration of chiral symmetry

Abstract The results of an extensive campaign of measurements of the π → π π process in the nucleon and nuclei at intermediate energies are presented. The measurements were motivated by the study of strong ππ correlations in nuclei. The analysis relies on the composite ratio C π π A , which accounts for the clear effect of the nuclear medium on the ππ system. The comparison of the C π π A distributions for the ( π π ) I = J = 0 and ( π π ) I = 0 , J = 2 systems to the model predictions indicates that the C π π A behavior in proximity of the 2 m π threshold is explainable through the partial restoration of chiral symmetry in nuclei.