QUARK STATES NEAR A THRESHOLD AND THE UNSTABLE H-DIBARYON

We consider the interplay of a quark state and a hadronic threshold in the framework of the P-matrix formalism, which is reviewed and extend ed for use together with conventional methods of computing quark-gluon dynamics, We provide a quantitative dynamical interpretation of the r educed R or K matrices and their poles that suggests a natural classif ication of threshold phenomena. At a threshold with a quark state clos e to it up to three S-matrix poles can be found. The scattering amplit udes for the corresponding cases are discussed. Our analysis is applie d to make an outlook for experimental observation of the doubly strang e H-dibaryon if it is not stable to strong decays, (C) 1997 Elsevier S cience B.V.