The Crystal Ball (CB) Collaboration at Brookhaven National Laboratory has recently presented results regarding a study of the ${\pi }^{-}\overrightarrow{A}{\pi }^0{\pi }^0{A}^{\prime }$ reaction on H, D, C, Al, and Cu, using a nearly $4\pi$ detector. Similar results, but for the ${\pi }^{+}\overrightarrow{A}{\pi }^{+}{\pi }^{\pm }{A}^{\prime }$ 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 ${\pi }^{+}{\pi }^{-}$ invariant mass spectra reported by the CHAOS group is also seen in the ${\pi }^0{\pi }^0$ CB data, when the results from the two groups are compared in a way which accounts for the different acceptances of the two experiments.

• Received 31 July 2001

DOI:https://doi.org/10.1103/PhysRevC.64.067601