Evidence for a narrow resonance at 1530 MeV/c2 in the K 0p-system of the reaction pp → Σ+K0p from the COSY-TOF experiment

The hadronic reaction pp→Σ+K0p was measured exclusively at a beam momentum of 2.95GeV/c using the TOF detector at the COSY storage ring. A narrow peak was observed in the invariant mass spectrum of the K0p-subsystem at 1530±5MeV/c2 with a significance of 4-6 standard deviations, depending on background assumptions. The upper limit of 18±4MeV/c2 (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) μb. Since a resonance in this subsystem must have strangeness S=+1 we claim it to be the Θ+ state for which very recently evidence was found in various experiments. © 2004 Elsevier B.V. All rights reserved.