Final State Interactions in Decays of the Exotic $\pi_{1}$ Meson

We analyze the role of final state interactions in decay of the lighest exotic meson, $pi_1$ with $J^{PC}=1^{-+}. We use the relativistic Lippmann-Schwinger equation for two coupled$\pi b_{1}$and$\pi\rho$channels. The first one is the predicted dominant decay mode of the$\pi_{1}$, whereas in the other a narrow$\pi_1(1600)$exotic signal has been reported by the E852 collaboration. The FSI potential is constructed, based on the$\omega$meson exchange between the two channels. We find that this process introduces corrections to the$\pi_{1}$widths of the order of only a few MeV. Therefore, we conclude that a substantial$\pi\rho$ mode cannot be generated through level mixing.