Meson production on complex nuclei by pi- with the Crystal Ball detector

final states allows an investigation of the nuclear final-state-interaction effects. The data show that nuclear absorption is mainly responsible for an observed change in the shape of the

2\pi^0

invariant mass spectra. Our preliminary result for the

\sigma \to \gamma \gamma

branching ratio is BR

(\sigma \to \gamma \gamma) < 3.6\times 10^{-3} \times \phi

at 90% C.L. on a carbon target, where

\phi

is the fraction of

2\pi^0

produced via the

\sigma

intermediate state.

Note:

Contribution to the International Workshop on Chiral Fluctuations in Hadronic Matter, Orsay, France, September 2001 (17 pages)

talk: Orsay 2001/09/26
pi- p: inclusive reaction
pi- nucleus: inclusive reaction
carbon
aluminum
copper
pi0: hadroproduction
eta: hadroproduction
mass spectrum: (2pi0)
f0(600): intermediate state

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