Deconfinement in the quark meson coupling model

Abstract

The Quark Meson Coupling Model which describes nuclear matter as a collection of non-overlapping MIT bags interacting by the self-consistent exchange of scalar and vector mesons is used to study nuclear matter at finite temperature. In its modified version, the density dependence of the bag constant is introduced by a direct coupling between the bag constant and the scalar mean field. In the present work, the coupling of the scalar mean field with the constituent quarks is considered exactly through the solution of the Dirac equation. Our results show that a phase transition takes place at a critical temperature around 200 MeV in which the scalar mean field takes a nonzero value at zero baryon density. Furthermore it is found that the bag constant decreases significantly when the temperature increases above this critical temperature indicating the onset of quark deconfinement.

Hot hypernuclear matter in the modified quark-meson coupling model

“…This indicates the onset of quark deconfinement above the critical temperature: at high enough temperature and/or baryon density there is a phase transition from the baryon-meson phase to the quark-gluon phase. This behaviour is also in qualitative agreement with our earlier results for SU(2) nuclear matter [18] except that the decrease here is more dramatic indicating that the phase transition is much stronger than in ordinary nuclear matter. Our results are also comparable to those obtained from lattice QCD calculations which have so far only explored the zero baryon density axis of the phase diagram in a meaningful way.…”

“…Moreover, the effective baryonic masses M * N,Λ,Σ,Ξ increase only slightly, if at all, with temperature up to about T = 150 MeV beyond which they decrease rapidly. This behaviour is qualitatively similar to our earlier results for normal nuclear matter [23,18,19] where the rapid decrease in the nucleon's effective mass was, however, found to start at rather higher temperatures T > 200 MeV. This rapid decrease of M * i with increasing temperature resembles a phase transition at high temperatures and low density, when the system becomes a dilute gas of baryons in a sea of baryon-antibaryon pairs [23].…”

“…We first solve Eqs. (18), (19), (20) and (21) self consistently for given values of temperature T and densities ρ B and ρ S to determine the baryonic and strangeness chemical potentials µ B and µ S , respectively. These constraints are given in terms of the effective baryon masses M * i which depend on the bag radii R i , the quark chemical potentials µ i q and the mean fields.…”

“…The quark chemical potential µ q , assuming that there are three quarks in the baryon bag, is determined from 3 = q n q where n q is the number of quarks of flavor q and is determined by [17][18][19]…”

“…The bag radius R i for baryon species i is obtained through the minimization of the baryon mass with respect to the bag radius [7,12,[17][18][19]]…”