Browsing by Author "Magdy, Niseem"

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On SU(3) Effective Models and Chiral Phase Transition
(HINDAWI LTD, 2015) Tawfik, Abdel Nasser; Magdy, Niseem
Sensitivity of Polyakov Nambu-Jona-Lasinio (PNJL) model and Polyakov linear sigma-model (PLSM) has been utilized in studying QCD phase-diagram. From quasi-particle model (QPM) a gluonic sector is integrated into LSM. The hadron resonance gas (HRG) model is used in calculating the thermal and dense dependence of quark-antiquark condensate. We review these four models with respect to their descriptions for the chiral phase transition. We analyze the chiral order parameter, normalized net-strange condensate, and chiral phase-diagram and compare the results with recent lattice calculations. We find that PLSM chiral boundary is located in upper band of the lattice QCD calculations and agree well with the freeze-out results deduced from various high-energy experiments and thermal models. Also, we find that the chiral temperature calculated from HRG is larger than that from PLSM. This is also larger than the freeze-out temperatures calculated in lattice QCD and deduced from experiments and thermal models. The corresponding temperature and chemical potential are very similar to that of PLSM. Although the results from PNJL and QLSM keep the same behavior, their chiral temperature is higher than that of PLSM and HRG. This might be interpreted due the very heavy quark masses implemented in both models.
SU(3) Polyakov linear-sigma model in magnetic fields: Thermodynamics, higher-order moments, chiral phase structure, and meson masses
(AMER PHYSICAL SOC, 2015) Tawfik, Abdel Nasser; Magdy, Niseem
Effects of an external magnetic field on various properties of quantum chromodynamics (QCD) matter under extreme conditions of temperature and density (chemical potential) have been analyzed. To this end, we use SU(3) Polyakov linear-sigma model and assume that the external magnetic field (eB) adds some restrictions to the quarks' energy due to the existence of free charges in the plasma phase. In doing this, we apply the Landau theory of quantization, which assumes that the cyclotron orbits of charged particles in a magnetic field should be quantized. This requires an additional temperature to drive the system through the chiral phase transition. Accordingly, the dependence of the critical temperature of chiral and confinement phase transitions on the magnetic field is characterized. Based on this, we have studied the thermal evolution of thermodynamic quantities (energy density and trace anomaly) and the first four higher-order moment of particle multiplicity. Having all these calculations, we have studied the effects of the magnetic field on the chiral phase transition. We found that both critical temperature T-c and critical chemical potential increase with increasing magnetic field, eB. Last but not least, the magnetic effects of the thermal evolution of four scalar and four pseudoscalar meson states are studied. We concluded that the meson masses decrease as the temperature increases up to T-c. Then, the vacuum effect becomes dominant and rapidly increases with the temperature T. At low T, the scalar meson masses normalized to the lowest Matsubara frequency rapidly decrease as T increases. Then, starting from T-c, we find that the thermal dependence almost vanishes. Furthermore, the meson masses increase with increasing magnetic field. This gives a characteristic phase diagram of T vs external magnetic field eB. At high T, we find that the masses of almost all meson states become temperature independent. It is worthwhile to highlight that the various meson states likely have different critical temperatures.
Thermodynamics and higher order moments in SU(3) linear sigma-model with gluonic quasiparticles
(IOP PUBLISHING LTD, 2015) Tawfik, Abdel Nasser; Magdy, Niseem
In the framework of the linear sigma-model (LSM) with three quark flavors, the chiral phase diagram at finite temperature and density is investigated. For temperatures higher than the critical temperature (T-c), we added to the LSM the gluonic sector from the quasi-particle model (QPM), which assumes that the interacting gluons in the strongly interacting matter, the quark-gluon plasma (QGP), are phenomenologically the same as non-interacting massive quasi-particles. The dependence of the chiral condensates of strange and non-strange quarks on the temperature and chemical potential is analyzed. Then, we calculate the thermodynamics in the new approach (using a combination of the LSM and the QPM). Confronting the results with those from recent lattice quantum chromodynamics simulations reveals an excellent agreement for almost all thermodynamic quantities. The dependences of the first-order and second-order moments of the particle multiplicity on the chemical potential at fixed temperature are studied. These investigations are implemented through characterizing the large fluctuations accompanying the chiral phase transition. The results for the first-order and second-order moments are compared with those from the SU(3) Polyakov linear sigma-model (PLSM). Also, the resulting phase diagrams deduced in the PLSM and the LSM+QPM are compared with each other.