Search for Exotic Baryons with Hidden Strangeness in the Experiments of the Sphinx Collaboration in Diffractive and Coulomb Production Processes

TL;DR

The SPHINX Collaboration's experiments identified potential new exotic baryon states with hidden strangeness, including a narrow resonance at 1807 MeV and an X(2000) candidate, suggesting possible cryptoexotic pentaquark structures.

Contribution

First experimental evidence of new baryon states with hidden strangeness in diffractive and Coulomb production processes, including detailed mass and width measurements.

Findings

Observation of a structure at 1807 MeV with narrow width.

Detection of an X(2000) peak with unusual decay properties.

Evidence supporting the existence of cryptoexotic pentaquark baryons.

Abstract

Experimental results of the SPHINX Collaboration on studying proton diffractive production processes are presented. Evidences for new baryon states with masses >1.8 GeV were obtained in hyperon-kaon effective mass spectra in several reactions. New data for the diffractive reaction p+N->[Sigma0 K+]+N at Ep=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(Sigma0 K+) a structure at the threshold region with a mass about 1800 MeV and a distinct X(2000) peak with M=1989+/-6 MeV and Gamma=91+/-20 MeV are observed. Unusual 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 a cryptoexotic pentaquark baryon with hidden strangeness |qqqs sbar>. We also present new results on the narrow threshold structure X(1810) with M=1807+/-7 MeV and Gamma=62+/-19 MeV which is produced in the region of very small pt**2<0.01 GeV**2. The possibility of the Coulomb production mechanism for X(1810) is discussed.