Evidence for a narrow resonance at 1530 MeV/c(2) in the K(0)p-system of the reaction pp ->Sigma(+)K(0)p from the COSY-TOF experiment

The hadronic reaction pp --> Sigma(+)K(0)p was measured exclusively at a beam momentum of 2.95 GeV/c using the TOF detector at the COSY storage ring. A narrow peak was observed in the invariant mass spectrum of the K(0)p-subsystem at 1530 +/- 5 MeV/c(2) with a significance of 4-6 standard deviations, depending on background assumptions. The upper limit of 18 +/- 4 MeV/c(2) (FWHM) for its width is given by the experimental resolution. The corresponding total cross section is estimated to be about 0.4 +/- 0.1 (stat) 0.1 (syst) mub. Since a resonance in this subsystem must have strangeness S = + I we claim it to be the Theta(+) state for which very recently evidence was found in various experiments. (C) 2004 Elsevier B.V. All rights reserved.