Isospin breaking and f0(980)-a0(980) mixing in the η(1405) → π0f0(980) reaction

Abstract

We make a theoretical study of the η(1405) → π0f0(980) and η(1405) → π0a0(980) reactions to determine the isospin violation and the mixing of the f0(980) and a0(980) resonances. We make use of the chiral unitary approach where these two resonances appear as dynamically generated by the meson-meson interaction provided by chiral Lagrangians. We obtain a very narrow shape for the f0(980) production in agreement with a BES experiment. As to the amount of isospin violation, assuming constant vertices for the primary η(1405) → π0KK̅ and η(1405) → π0π0η production, we find results which are much smaller than found in the experimental BES paper. The problem is solved by using the primary production driven by η' → K*K̅ followed by K∗→ Kπ. Thus, we can predict absolute values for the ratio Γ(π0,π+π−)/Γ(π0,π0η) which are in fair agreement with experiment.