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IHEP 98 - 29
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| L.G. Landsberg | ||
| Searh for Exotic Baryons with Hidden Strangeness in the Experiments of the Sphinx Collaboration in Diffractive and Coulomb Production Processes | ||
| Protvino, 1999.-p.23, figs.14, tables 11, refs.:28. | ||
Experimental results of the SPHINX Collaboration on studying proton diffractive production processes at $E_p$=70~GeV are presented. Evidences for new baryon states with masses $\gtrsim~1.8$~GeV were obtained in hyperon-kaon effective mass spectra in several reactions. New data for the diffractive reaction $p+N \rightarrow [\Sigma^oK^+]+N$ at $E_p=70$~GeV were obtained with partially upgraded SPHINX setup. The data are in a good agreement with the results of our previous study of this reaction. In the mass spectrum $M(\Sigma^oK^+)$ a structure at the threshold region with a mass $\sim 180$~MeV and a distinct $X(2000)$ peak with $M=1989\pm 6$~MeV and $\Gamma=91\pm20$~MeV are observed. Unusual dynamical features of the massive $X(2000)$ state (narrow decay width, anomalously large branching ratio for the decay channel with strange particle emission) make it a serious candidate for cryptoexotic pentaquark baryon with hidden strangeness $|qqqs \bar s>$. We also present new results on the narrow threshold structure $X(1910)$ with $M=1807 \pm 7$~MeV and $\Gamma = 62 \pm 19$~MeV which is produced in the region of very small $p^2_T<0.01$~GeV$^2$. The possibility of the Coulomb production mechanism for $X(1800)$ is discussed.
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