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Register a new userEffective model approach to meson screening masses at finite temperature
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Temperature dependence of pion and sigma-meson screening masses is evaluated by the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model with the entanglement vertex. We propose a practical way of calculating meson screening masses in the NJL-type effective models. The method based on the Pauli-Villars regularization solves the well-known difficulty that the evaluaton of screening masses is not easy in the NJL-type effective models.The PNJL model with the entanglement vertex and the Pauli-Villars regularization well reproduces lattice QCD results on temperature dependence of the chiral condensate and the Polyakov loop. The method is applied to analyze temperature dependence of pion screening mass calculated with state-of-the-art lattice simulations with success in reproducing the lattice QCD results.
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Temperature dependence of pion and sigma-meson screening masses is evaluated by the Polyakov-loop extended Nambu--Jona-Lasinio model with the entanglement vertex (EPNJL model). We propose a practical way of calculating meson screening masses in the NJL-type effective models. The method based on the Pauli-Villars regularization solves the well-known difficulty that the evaluation of screening masses is not easy in the NJL-type effective models. The method is applied to analyze temperature dependence of pion screening masses calculated with state-of-the-art lattice simulations with success in reproducing the lattice QCD results. We predict the temperature dependence of pole mass by using EPNJL model.
We first extend our formulation for the calculation of $pi$- and $sigma$-meson screening masses to the case of finite chemical potential $mu$. We then consider the imaginary-$mu$ approach, which is an extrapolation method from imaginary chemical potential ($mu=i mu_{rm I}$) to real one ($mu=mu_{rm R}$). The feasibility of the method is discussed based on the entanglement Polyakov-loop extended Nambu--Jona-Lasinio (EPNJL) model in 2-flavor system. As an example, we investigate how reliable the imaginary-$mu$ approach is for $pi$- and $sigma$-meson screening masses, comparing screening masses at $mu_{rm R}$ in the method with those calculated directly at $mu_{rm R}$. We finally propose the new extrapolation method and confirm its efficiency.
We report on the first study of the screening properties of the mesonic excitations with strange ($s$) and charm ($c$) quarks, specifically the ground states of the pseudo-scalar and vector meson excitations for the $bar{s}s$, $bar{s}c$ and $bar{c}c$ flavor combinations, using the Highly Improved Staggered Quark action with dynamical physical strange quark and nearly-physical up and down quarks. By comparing with their respective vacuum meson masses and by investigating the influence of the changing temporal boundary conditions of the valence quarks we study the thermal modifications of these mesonic excitations. While the $bar{s}s$ states show significant modifications even below the chiral crossover temperature $T_c$, the modifications of the open-charm and charmonium like states become visible only for temperatures $Tgtrsim T_c$ and $Tgtrsim1.2T_c$, respectively.
We propose a practical effective model by introducing temperature ($T$) dependence to the coupling strengths of four-quark and six-quark Kobayashi-Maskawa-t Hooft interactions in the 2+1 flavor Polyakov-loop extended Nambu-Jona-Lasinio model. The $T$ dependence is determined from LQCD data on the renormalized chiral condensate around the pseudocritical temperature $T_c^{chi}$ of chiral crossover and the screening-mass difference between $pi$ and $a_0$ mesons in $T > 1.1T_c^chi$ where only the $U(1)_{rm A}$-symmetry breaking survives. The model well reproduces LQCD data on screening masses $M_{xi}^{rm scr}(T)$ for both scalar and pseudoscalar mesons, particularly in $T ge T_c^{chi}$. Using this effective model, we predict meson pole masses $M_{xi}^{rm pole}(T)$ for scalar and pseudoscalar mesons. For $eta$ meson, the prediction is consistent with the experimental value at finite $T$ measured in heavy-ion collisions. We point out that the relation $M_{xi}^{rm scr}(T)-M_{xi}^{rm pole}(T) approx M_{xi}^{rm scr}(T)-M_{xi}^{rm pole}(T)$ is pretty good when $xi$ and $xi$ are scalar mesons, and show that the relation $M_{xi}^{rm scr}(T)/M_{xi}^{rm scr}(T) approx M_{xi}^{rm pole}(T)/M_{xi}^{rm pole}(T)$ is well satisfied within 20% error when $xi$ and $xi$ are pseudoscalar mesons and also when $xi$ and $xi$ are scalar mesons.
We incorporate the effective restoration of $U(1)_{rm A}$ symmetry in the 2+1 flavor entanglement Polyakov-loop extended Nambu--Jona-Lasinio (EPNJL) model by introducing a temperature-dependent strength $K(T)$ to the Kobayashi-Maskawa-t Hooft (KMT) determinant interaction. $T$ dependence of $K(T)$ is well determined from pion and $a_0$-meson screening masses obtained by lattice QCD (LQCD) simulations with improved p4 staggered fermions. The strength is strongly suppressed in the vicinity of the pseudocritical temperature of chiral transition. The EPNJL model with the $K(T)$ well reproduces meson susceptibilities calculated by LQCD with domain-wall fermions. The model shows that the chiral transition is second order at the light-quark chiral-limit point where the light quark mass is zero and the strange quark mass is fixed at the physical value. This indicates that there exists a tricritical point. Hence the location is estimated.
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