The $K^-\pi^+$ S-wave from the $D^+ \to K^-\pi^+\pi^+$ decay

Using data from FOCUS (E831) experiment at Fermilab, we present a model independent partial-wave analysis of the K−π+ S-wave amplitude from the decay D+→K−π+π+ . The S-wave is a generic complex function to be determined directly from the data fit. The P- and D-waves are parameterized by a sum of Breit–Wigner amplitudes. The measurement of the S-wave amplitude covers the whole elastic range of the K−π+ system.