Decays of Photons and Neutrinos within Nuclei

According to present theories of the dipersion relation for a $\pi$ meson within nuclear matter, decays such as $\gamma \to {\pi }^{+}+{\pi }^{-}$ and $\overline{\nu }\to e^{+}+{\pi }^{-}$ are allowed within nuclei. Observation of nuclear processes instigated by these decays can provide information on the pion dispersion relations and on weak and electromagnetic form factors in nuclear matter.