π→ππresults in nuclei

The Crystal Ball (CB) Collaboration at Brookhaven National Laboratory has recently presented results regarding a study of the ${\ensuremath{\pi}}^{\ensuremath{-}}\stackrel{\ensuremath{\rightarrow}}{A}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{A}^{\ensuremath{'}}$ reaction on H, D, C, Al, and Cu, using a nearly $4\ensuremath{\pi}$ detector. Similar results, but for the ${\ensuremath{\pi}}^{+}\stackrel{\ensuremath{\rightarrow}}{A}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}{A}^{\ensuremath{'}}$ reaction on ${}^{2}\mathrm{H},$ ${}^{12}\mathrm{C},$ ${}^{40}\mathrm{Ca},$ and ${}^{208}\mathrm{Pb},$ have been published earlier by the CHAOS Collaboration at TRIUMF. In this Brief Report a comparison of the results of the two measurements is made, which shows that the CHAOS and CB data share relevant common features. In particular, the increase in strength as a function of A seen in the near-threshold ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ invariant mass spectra reported by the CHAOS group is also seen in the ${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ CB data, when the results from the two groups are compared in a way which accounts for the different acceptances of the two experiments.