In medium sigma meson effects in two pion photoproduction in nuclei

Abstract

We show theoretical results for $(\gamma ,{\pi }^0{\pi }^0)$ production on nucleons and nuclei in the kinematical region where the scalar isoscalar $\pi \pi$ amplitude is influenced by the $\sigma$ 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 $\sigma$ pole to lower masses and widths as the nuclear density increases.

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