Properties of dense strange hadronic matter with quark degrees offreedom

Abstract

The properties of strange hadronic matter are studied in the context ofthe modified quark-meson coupling model using two substantiallydifferent sets of hyperon-hyperon (YY) interactions. The first set isbased on the Nijmegen hard-core potential model D with slightlyattractive YY interactions. The second potential set is based on therecent SU(3) extension of the Nijmegen soft-core potential NSC97 withstrongly attractive YY interactions which may allow for deeply boundhypernuclear matter. The results show that, for the first potential set,the Σ hyperon does not appear at all in the bulk at any baryondensity and for all strangeness fractions. The binding energy curves of theresulting NΛΞ system vary smoothly with density and thesystem is stable (or metastable if we include the weak force). However,the situation is changed drastically when using the second set where theΣ hyperons appear in the system at large baryon densities above acritical strangeness fraction. We find that strange hadronic matter undergoes afirst-order phase transition from an NΛΞ system to anNΣΞ system for strangeness fractions fS>1.2 and baryonic densitiesexceeding twice the ordinary nuclear matter density. Furthermore, it is foundthat the system built of NΣΞ is deeply bound. This phasetransition affects the equation of state significantly, which becomes muchsofter and a substantial drop in energy density and pressure are detectedas the phase transition takes place.