Searches for exotic pentaquark baryons with hidden strangeness in experiments at the SPHINX facility

The results obtained by experimentally studying the reactions of diffractiv e particle production with the SPHINX facility have been discussed. The exp eriments have been performed in a proton beam from the 70-GeV accelerator i nstalled at the Institute for High Energy Physics (IHEP, Protvino, Russia). Searches for exotic pentaquark baryons with hidden stangeness in diffracti ve production processes have been considered. Basic results have been obtai ned for the reaction p + N --> [Sigma(0)K(+)] + N, where the effective-mass spectrum M(Sigma(0)K(+)) has been found to be dominated by a peak with par ameters M = 1989 +/- 6 MeV and Gamma = 91 +/- 20 MeV. The anomalous propert ies of this state render it a serious candidate for exotic baryons, Additio nal data supporting the existence of this baryon have been discussed.