Nonlocal SU(3) chiral quark models at finite temperature: the role of the Polyakov loop

We analyze the role played by the Polyakov loop in the description of the chiral phase transition within the framework of nonlocal SU(3) chiral models with flavor mixing. We show that its presence provides a substantial enhancement of the predicted critical temperature, bringing it to a better agreement with the most recent results of lattice calculations.Comment: 9 pages, 1 figur

The hadronic off-shell width of meson resonances

Within the resonance chiral effective theory we study the dressed propagators of the spin-1 fields, as arise from a Dyson-Schwinger resummation perturbatively constructed from loop diagrams with absorptive contributions in the s-channel. We apply the procedure to the vector pion form factor and the elastic pion-pion scattering to obtain the off-shell width of the rho_0 meson. We adopt a definition of the off-shell width of spin-1 meson resonances that satisfies the requirements of analyticity, unitarity, chiral symmetry and asymptotic behaviour ruled by QCD. To fulfil these constraints the resummation procedure cannot consist only of self-energy diagrams. Our width definition is shown to be independent of the formulation used to describe the spin-1 meson resonances.Comment: 1+12 pages, 4 figures. Minor changes in text. Conclusions unchanged. Version accepted for publication in Phys. Rev.

Light pseudoscalar mesons in a nonlocal SU(3) chiral quark model

We study the properties of the light pseudoscalar mesons in a three flavor chiral quark model with nonlocal separable interactions. We concentrate on the evaluation of meson masses and decay constants, considering both the cases of Gaussian and Lorentzian nonlocal regulators. The results are found to be in quite good agreement with the empirical values, in particular in the case of the ratio f_K/f_pi and the anomalous decay pi^0 --> gamma gamma. In addition, the model leads to a reasonable description of the observed phenomenology in the eta-eta' sector, even though it implies the existence of two significantly different state mixing angles.Comment: 18 pages, 3 figures. New subsections included, references added. Mixing angles eta - eta' reanalyzed. Final version to appear in Phys. Rev.

Main phenomenological features of the spontaneous CP violation in SU(3) x U(1) models

We analyze the phenomenological consequences of assuming spontaneous CP violation in an SU(3) x U(1) model with three Higgs triplets and one sextuplet. After the identification of the relevant physical scalars, we estimate the contributions to the parameters $\Delta m_K$, $\epsilon$ and $\epsilon'$ coming from the Higgs-fermion couplings.Comment: 21 pages RevTex, epsf, epsfig, 4 figure

Charged pion masses under strong magnetic fields in the NJL model

The behavior of charged pion masses in the presence of a static uniform magnetic field is studied in the framework of the two-flavor NJL model, using a magnetic field-independent regularization scheme. Analytical calculations are carried out employing the Ritus eigenfunction method, which allows us to properly take into account the presence of Schwinger phases in the quark propagators. Numerical results are obtained for definite model parameters, comparing the predictions of the model with present lattice QCD results.Fil: Coppola, Máximo. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia Física (Centro Atómico Constituyentes). Proyecto Tandar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gomez Dumm, Daniel Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Scoccola, Norberto Nerio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Favaloro; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia Física (Centro Atómico Constituyentes). Proyecto Tandar; Argentin

Meson properties at finite temperature in a three flavor nonlocal chiral quark model with Polyakov loop

We study the finite temperature behavior of light scalar and pseudoscalar meson properties in the context of a three-flavor nonlocal chiral quark model. The model includes mixing with active strangeness degrees of freedom, and takes care of the effect of gauge interactions by coupling the quarks with the Polyakov loop. We analyze the chiral restoration and deconfinement transitions, as well as the temperature dependence of meson masses, mixing angles and decay constants. The critical temperature is found to be T_c = 202 MeV, in better agreement with lattice results than the value recently obtained in the local SU(3) PNJL model. It is seen that above T_c pseudoscalar meson masses get increased, becoming degenerate with the masses of their chiral partners. The temperatures at which this matching occurs depend on the strange quark composition of the corresponding mesons. The topological susceptibility shows a sharp decrease after the chiral transition, signalling the vanishing of the U(1)_A anomaly for large temperatures.Comment: 21 pages, 4 figures. Fig. 3 and final part of Sect. IV modified, references added, conclusions unchanged. To be published in Phys. Rev.