We report on an investigation of the $({\pi }^{-},{\pi }^0{\pi }^0)$ reaction by means of measurements of the ${\pi }^0{\pi }^0$ invariant mass distributions from ${\pi }^{-}$ interactions on H, D, C, Al, and Cu targets at $p_{{\pi }^{-}}=0.408\mathrm{}\mathrm{GeV}/c$. The sharp, strong peak in the ${\pi }^{+}{\pi }^{-}$ invariant mass near ${2m}_{\pi }$ reported by the CHAOS Collaboration is not seen in our ${\pi }^0{\pi }^0$ data. However, we do observe a change in the shape of the ${\pi }^0{\pi }^0$ invariant mass spectrum for the different targets, indicating that the ${\pi }^0{\pi }^0$ interaction diminishes in the nuclear medium as represented by nuclei D, C, Al, and Cu, compared to hydrogen.

• Received 1 May 2000

DOI:https://doi.org/10.1103/PhysRevLett.85.5539