Matching the QCD and Hadron Sectors and Medium Dependent Meson Masses; Hadronization in Relativistic Heavy Ion Collisions

The recent developments on the “vector manifestation” of chiral symmetry by Harada and Yamawaki provide a compelling evidence for, and “refine,” the in-medium scaling of hadronic properties in dense/hot matter (call it “BR scaling”) proposed by the authors in 1991. We reinterpret the Harada-Yamawaki result obtained in a Wilsonian renormalization-group approach to hidden local symmetry theory matched to QCD at near the chiral scale in terms of Nambu-Jona-Lasinio model and predict that the vector meson mass in medium should scale mρ/mρ ∼ (〈q̄q〉⋆/〈q̄q〉)1/2 from n = 0 up to ∼ n = n0 (where n0 is nuclear matter density) and then go over to the linear scaling mρ/mρ ∼ 〈q̄q〉⋆/〈q̄q〉 up to the chiral transition density nc at which the mass is to vanish (in the chiral limit) according to the vector manifestation fixed point. In the regime of the linear scaling above n0, the (vector) gauge coupling constant should fall linearly in 〈q̄q〉⋆, vanishing at the critical point, with the width of the vector meson becoming steeply narrower. We suggest the in-medium vector meson mass, both parametric and pole, which goes smoothly to zero with increasing density, to be an order parameter for chiral symmetry restoration and the RHIC observation of rough equality of outward and sideways Hanbury Brown-Twiss (HBT) radii as an experimental indication of equilibration as the hadrons go back on shell. Some other issues related to recent RHIC observations are qualitatively discussed in the appendices. Our main conclusion that follows from these considerations is that the movement towards chiral restoration can be reliably described in Nambu-Jona-Lasinio mean field, with constituent quarks as variables, although there is probably density discontinuity following chiral restoration. ∗and School of Physics, Korea Institute for Advanced Study, Seoul 130-012, Korea