“Free” constituent quarks and dilepton production in heavy-ion collisions

Abstract

An approach is suggested, invoking vitally the notion of constituent massive quarks (valons) which can survive and propagate rather than hadrons (except of pions) within the hot and dense matter formed below the chiral transition temperature in course of the heavy ion collisions at high energies. This approach is shown to be quite good for description of the experimentally observed excess in dilepton yield at masses 250 MeV ≤ M ee ≤ 700 MeV over the prompt resonance decay mechanism (CERES cocktail) predictions. In certain aspects, it looks to be even more successful, than the conventional approaches: it seems to match the data somewhat better at dilepton masses before the two-pion threshold and before the ρ-meson peak as well as at higher dilepton masses (beyond the φ-meson one). The approach implies no specific assumptions on the equation of state (EOS) or peculiarities of phase transitions in the expanding nuclear matter.

Color deconfinement and subhadronic matter: phase states and the role of constituent quarks

“…If we consider the long QpK-phase instead of the longlived hadron phase (just as we did in the above description of the secondary hadron fractional yields), then we obtain a theoretical explanation [60] of the dileptonic spectrum that is, at least, no worse, while seeming sometimes even somewhat better: it follows more accurately the experimental data at M ee 9 2m p and M ee 5 1 GeV (see the bold curves in Figs 13 and 14a). Within this approach, dileptonic excess over the CERES-cocktail 34 results from their generation in the course of the enormous reiteration of the prompt pp-and Q " Q-collisions over the long evolution of the QpK-phase.…”

“…The combinatorial method of calculation (see Ref. [60] for this and other details) essentially coincides with what was done in calculating the yield of the different hadron species, and we therefore give only the final formula, in which a certain effective temperature (close to its averages in between the chiral transition and hadronization temperatures), hT i 160 MeV, and the corresponding mean free time, Figure 13. Comparing the models with the experimental data [56,57] on the yield of dileptons (e e À pairs) with small invariant masses.…”

“…Comparing the models with the experimental data [56,57] on the yield of dileptons (e e À pairs) with small invariant masses. The results obtained within the intermediate-phase scenario [60] (the solid and dashed bold curves refer to m p 140 MeV and tahti 20 and to the averaged inmedium pion mass m p 100 MeV, and tahti 30, respectively) are compared to the results obtained ignoring this phase [58] (the thin curves).…”

Quarkyonic matter and chiral symmetry breaking

“…The significance of this conclusion is subject to many uncertainties. One cannot therefore with certainty conclude nor rule out, that there is an intermediate phase of unconfined constituent quarks, as has been argued by Feinberg et al [21]. In any case, the position of the chiral and the quarkyonic phase occur at numerically close, or perhaps identical, values of µ.…”

“…Until very recently, the possible new physics in the QCD phase diagram were Color Superconducting phases which might be important at asymptotically high baryon number density and low temperatures [14]. In addition, a combination of efforts of Lattice Gauge Theory (LGT) [15] and effective model calculations [16,17,18,19,20,21] have given new insight on the position, the order and the universal properties [22] of the QCD phase diagram.…”