STUDY OF COHERENT DIFFRACTIVE PRODUCTION REACTIONS OF P-][Y(0)K(+)]+CTYPE AND OBSERVATION OF NARROW STRUCTURES IN SIGMA(1385)K-O(+) AND SIGMA-K-O(+) EFFECTIVE-MASS SPECTRA(C)

In the experiments at the SPHINX facility in 70 GeV proton beam of the IHEP accelerator the coherent diffractive production reactions on car bon nuclei p + C --> [Sigma(1385)K-o(+)] + C and p + C --> [Sigma(o)K( +)] + C were investigated. The evidences for new baryon states were ob tained in the study of hyperon-kaon effective mass spectra in these tw o reactions: X(2050) with mass M = (2052 +/- 6) MeV and width Gamma = (35 (+22)(-35)) MeV in M[Sigma(1385)K-o(+)] and X(2000) with M = 1999 +/- 6 MeV and Gamma = 91 +/- 17 MeV in M[Sigma(o)K(+)]. The unusual fe atures of these massive states (small enough decay widths, anomalously large branching ratios for decays with strange particles-emission) ma ke them very serious candidates for cryptoexotic pentaquark baryons wi th hidden strangeness.