In medium sigma meson effects in two pion photoproduction in nuclei

Abstract

We show theoretical results for $(γ, π^0 π^0)$ production on nucleons and nuclei in the kinematical region where the scalar isoscalar $ππ$ amplitude is influenced by the $σ$ pole. The final state interaction of the pions modified by the nuclear medium produces a spectacular shift of strength of the two pion invariant mass distribution induced by the moving of the $σ$ pole to lower masses and widths as the nuclear density increases.

Contribution to the XVIth International Conference on Particles and Nuclei (PANIC02), Osaka, Japan, 30 September 4 October 2002. 4 pages, 1 figure