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

Abstract

We report on preliminary results for the production of neutral mesons by 750 MeV/$c$ ${\pi }^{-}$ on complex nuclear targets (C, Al, Cu) and hydrogen. Our simultaneous measurement of ${\pi }^0$, $2{\pi }^0$, and $\eta$ 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$(\sigma \to \gamma \gamma )<3.6\times 10^{-3}\times \varphi$ at 90% C.L. on a carbon target, where $\varphi$ is the fraction of $2{\pi }^0$ produced via the $\sigma$ intermediate state.

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

Cited by in corpus (1)

• The $({\pi }^{-},\gamma \gamma )$ reaction in nuclei and the $\sigma$ meson in the medium