N ov 2 00 4 Final State Interactions in Hadronic D decays

We show that the large corrections due to final state interactions (FSI) in the D+ → π−π+π+ , D+ s → π−π+π+ , and D+ → K−π+π+ decays can be accounted for by invoking scattering amplitudes in agreement with those derived from phase shifts studies. In this way, broad/overlapping resonances in S-waves are properly treated and the phase motion of the amplitudes are driven by the corresponding scattering phase shifts determined in many other experiments. This is an important step forward in resolving the puzzle of the FSI in these decays. We also discuss why the σ and κ resonances, hardly visible in scattering experiments, are much more prominent and clearly visible in these decays without destroying the agreement with the experimental ππ and Kπ low energy S-wave phase shifts.