Double neutral pion photoproduction at threshold

Abstract

We consider the chiral expansion of the threshold amplitude for the reaction $\gamma p\to {\pi }^0{\pi }^{0}p$ to order $\mathcal{O}(M_{\pi }^2)$. We substantiate a claim that this photoproduction channel is significantly enhanced close to threshold due to pion loops. A precise measurement of the corresponding cross sections is called for which allows to test chiral perturbation theory.

Comments: 8 pp, LaTeX