The Crystal Ball (CB) collaboration at BNL has recently presented results
regarding a study of the π−A→π0π0A′ reaction on H,D,C,Al and Cu, using a nearly 4π detector. Similar results, but for the
π+A→π+π±A′ reaction on 2H, 12C, 40Ca,
and 208Pb, 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 π+π− invariant mass spectra reported by the
CHAOS group, is also seen in the π0π0 CB data, when the results from
the two groups are compared in a way which accounts for the different
acceptances of the two experiments.Comment: 7 pages, 1 figure, accepted for publication in Phy. Rev. C - Brief
Repor