EVIDENCEFORp(1300)IN THEREACTION K-p+dn--A AT llGeV/c *

Results are presented from an analysis of the r+rrsystem produced in the reaction K-p + n+r-R at 11 GeV/c observed with the LASS Spectrometer at SLAC. A clear p-w interference effect is observed, and a fit to the natural parity exchange mass distribution yields an estimate of (1.5 f 0.5)% for the branching fraction of the decay w --f r + x -. An amplitude analysis reveals that the bump in the mass distribution in the vicinity of the f2( 1270) actually contains a significant P-wave component. The mass dependence of the corresponding amplitude and phase is well described by a resonant Breit-Wigner line shape with mass (1290?$$ MeV/c2, width (120?:$ MeV/c2, and small 7r+7relasticity. The interpretation of this state as the first radial excitation of the ~(770) is discussed. Evidence is presented for production of the ps(1690) in the r+rspectrum. Submitted to Zeitschrift fiir Physik C *Work supported in part by the Department of Energy under contract No. DE-AC03-76SF00515, the National Science Foundation under grant No. PHY92-04239, and the Japan U.S. Cooperative Research Project on High Energy Physics. 12-w 0 4 8 12 M2,+,c[ (GeV/c2)2] Fig. 1. The Dalitz plot for the events of reaction (1) with -&,A 2 2(GeV/c)2.