The $K \bar K π$ decay of the $f_1(1285)$ and its nature as a $K^* \bar K -cc$ molecule

Abstract

We investigate the decay of $f_1(1285) \to πK \bar K$ with the assumption that the $f_1(1285)$ is dynamically generated from the $K^* \bar{K} - cc$ interaction. In addition to the tree level diagrams that proceed via $f_1(1285) \to K^* \bar{K} - cc \to πK \bar K$, we take into account also the final state interactions of $K \bar K \to K \bar K$ and $πK \to πK$. The partial decay width and mass distributions of $f_1(1285) \to πK \bar K$ are evaluated. We get a value for the partial decay width which, within errors, is in fair agreement with the experimental result. The contribution from the tree level diagrams is dominant, but the final state interactions have effects in the mass distributions. The predicted mass distributions are significantly different from phase space and tied to the $K^* \bar{K} - cc$ nature of the $f_1(1285)$ state.