Hadron to quark—gluon phase transition in the baryon-rich domain

Abstract

The hadron to quark-gluon phase transition is studied in charge symmetric matter. Nuclear field theory describes the hadronic phase, including baryon resonances and thermal pions and kaons. The pion dispersion in medium is computed. The other phase is described as a gas of massless u and d quarks and gluons and massive s quarks, with or without gluon exchange .. The RankineHugoniot relation is employed to estimate the initial properties of matter produced in nuclear collisions as a function of energy. It is found that signals depending on pressure or entropy are poor ones and that the most dramatic differences between the hadronic phase and mixed phase occur in the temperature and density. Di-lepton and photon signals ought therefore to be good ones. It is shown that the analogy of "melting" of hadrons in the plasma is incorrect as concerns formation of a plasma in nuclear collisions in contrast to the adiabatic heating of matter. Neither the phase diagram nor the properties of matter on the shock trajectory depend very much on the nuclear equation of state within the uncertainties with which it can be defined in terms of conventional nuclear saturation properties, because the thermal energy dominates over these. The main dependances are on the hadron spectrum, the pion dispersion in medium, the bag constant and the QCD coupling constant. Within accepted uncertainties in the nuclear and plasma equations of state, the mixed · phase could be formed in collisions with laboratory kinetic energy as low as 2.5 GeV.PACS 21.65+£, 25.70.Np, 0570.Fh tThis work was supported by the

Excitation functions in central Au+Au collisions from SIS/GSI to AGS/Brookhaven

“…Among the proposed experiments we are particularly interested in those by the E895 and E866 collaboration which will carry out extensive systematic studies at several beam momenta between 2 and 12 GeV/c using a Au beam [5,6]. These experiments are interesting and important as it has been predicted based on hydrodynamical models that the QGP phase transition may occur in heavy-ion collisions at energies between E lab /A= 2-10 GeV [7,8]. Also, theoretical studies (e. g. [9][10][11][12][13]) have shown that the properties of hadrons, such as their masses and decay widths, may be modified in hot dense hadronic matter as a result of the partial restoration of chiral symmetry.…”

“…The maximum compression attainable in a heavy-ion collision can be obtained by either solving the Rankine-Hugoniot (RH) equation [33] (e.g., in refs. [34,29,35,36]) or directly seeking for approximate solutions of the hydrodynamical equations (e.g., in refs. [37,38]).…”

Bombarding Energy Dependence ofπ−Interferometry at the Brookhaven AGS

“…Heavy ion reaction studies at Brookhaven's Alternating Gradient Synchrotron (AGS) probe nuclear matter at very high baryon density (r ϳ 6 8r 0 ) [14,15]. Some models [14][15][16][17][18] and equilibrium-based metaanalyses of data [19] suggest that sufficient energy density may be generated in collisions below maximum AGS energies to trigger QGP formation. Hydrodynamic calculations suggest an HBT excitation function as an excellent method to detect the transition to QGP through a sudden increase of emission time scale [13].…”

Subthreshold kaon production and the nuclear equation of state

“…(2), in the relativistic approach the EOS at high densities largely depends on the vector repulsion from the omega meson. From the Hugenholtz-Van Hove theorem, which requires that the Fermi energy is equal to the average single particle energy at saturation, we have the following relation [12] g…”