Investigation of the diffractive reaction p+N→[Σ+K0]+N at the proton energy of Ep=70 GeV and observation of the decay process X(2000)→Σ+K0

The diffractive reaction p + N --> [Sigma(+)K(0)] + N induced by 70-GeV protons is investigated at the SPHINX facility. The measured mass spectrum of the Sigma(+)K(0) system originating from this reaction shows a resonance structure with a mass of M = 1995 +/- 18 MeV and a width of Gamma = 90+/-32 MeV. The cross section for the formation of this structure is found to be sigma = 182 +/- 38 nb per target nucleon. These data comply well with the results that we obtained previously in studying the reaction p + N --> [Sigma(0)K(+)] + N, where we observed the formation of the X(2000) --> Sigma(0)K(+) state, a candidate for an exotic baryon with hidden strangeness. The measured ratio R of the two branching fractions, R = Br[X(2000) --> Sigma(+)K(0)]/Br[X(2000) --> Sigma(0)K(+)] = 1.91 +/- 0.38, is conisistent with the value of R = 2 expected for an isospin-1/2 baryon. (C) 2000 MAIK "Nauka/Interperiodica".