Small size pentaquark in QCD sum rule approach

Abstract

The analysis of the sum rules (for two differentchoices of 5-quark currents) indicate that to explain experimental results it is necessary to have some one-particle lower state (and pentaquark is a reliable candidate to this state) while the two-particle coupled lower state ($NK$ system) should be excluded. Obtained sum rules have good stability and correspond to pentaquark mass $m_\theta$=1.54 $GeV$ at the appropriate choice of continuum threshold. Also the features of the sum rules for 2-point correlator with 5-quark currents are studied. This features should be taken into account to obtain sum rules correctly.