Chiral dynamics in "gamma p --> pi^0 eta p" and related reactions

Abstract

Using a chiral unitary approach for meson-baryon scattering in the strangeness zero sector, where the $N^{\ast }(1535)$ and ${\Delta }^{\ast }(1700)$ resonances are dynamically generated, we study the reactions $\gamma p\to {\pi }^0\eta p$ and $\gamma p\to {\pi }^0{K}^0{\Sigma }^{+}$ at photon energies at which the final states are produced close to threshold. Among several reaction mechanisms, we find the most important is the excitation of the ${\Delta }^{\ast }(1700)$ state which subsequently decays into a pseudoscalar meson and the $N^{\ast }(1535)$. Hence, the reaction provides useful information with which to test current theories of the dynamical generation of the low-lying $1/2^{-}$ and $3/2^{-}$ states. Predictions are made for cross sections and invariant mass distributions which can be compared with forthcoming experiments at ELSA.

Comments: Talk given at the "Eta05" conference, Cracow, 09-16-2005, 4 pages, 3 figures