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.
In the framework of the Nambu–Jona-Lasino (NJL) model, we study the effect of an intense external uniform magnetic field on neutral and charged pion masses and decay form factors. In particular, the ...treatment of charged pions is carried out on the basis of the Ritus eigenfunction approach to magnetized relativistic systems. Our analysis shows that in the presence of the magnetic field three and four nonvanishing pion-to-vacuum hadronic form factors can be obtained for the case of the neutral and charged pions, respectively. As expected, it is seen that for nonzero magnetic field the π0 meson can still be treated as a pseudo Nambu-Goldstone boson, and consequently the corresponding form factors are shown to satisfy various chiral relations. For definite parametrizations of the model, numerical results for π0 and π± masses and decay constants are obtained and compared with previous calculations given in the literature.
We study the behavior of neutral meson properties in the presence of a static uniform external magnetic field in the context of nonlocal chiral quark models. The formalism is worked out introducing ...Ritus transforms of Dirac fields, which allow to obtain closed analytical expressions for π0 and σ meson masses and for the π0 decay constant. Numerical results for these observables are quoted for various parametrizations. In particular, the behavior of the π0 meson mass with the magnetic field is found to be in good agreement with lattice QCD results. It is also seen that the Goldberger-Treiman and Gell-Mann-Oakes-Renner chiral relations remain valid within these models in the presence of the external magnetic field.
We study the behavior of strongly interacting matter under an external constant magnetic field in the context of nonlocal chiral quark models within the mean field approximation. We find that at zero ...temperature the behavior of the quark condensates shows the expected magnetic catalysis effect, our predictions being in good quantitative agreement with lattice QCD results. On the other hand, in contrast to what happens in the standard local Nambu-Jona-Lasinio model, when the analysis is extended to the case of finite temperature, our results show that nonlocal models naturally lead to the inverse magnetic catalysis effect.
We analyze the features of strongly interacting matter in the presence of nonzero isospin chemical potential μI, within a nonlocal two-flavor Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model. ...For a system at finite temperature T, we describe the behavior of various thermodynamic quantities and study the phase diagram in the μI − T plane. In particular, it is found that for values of μI larger than the pion mass and temperatures lower than a critical value of about 170 MeV the system lies in an isospin symmetry broken phase signalled by the presence of a nonzero pion condensate. Our results for the phase diagram are found to be in better agreement with those arising from lattice QCD calculations, as compared to the predictions from other theoretical approaches like the local PNJL model.
The behavior of π0 meson properties in the presence of a uniform external magnetic field is studied in the context of a nonlocal extension of the Polyakov-Nambu-Jona-Lasinio model. The analysis ...includes the π0 mass, the effective π0-quark coupling and the pion-to-vacuum hadronic form factors, both at zero and finite temperature. Numerical results are compared with previous calculations carried out within the local NJL model, when available. The validity of chiral relations and the features of deconfinement and chiral symmetry restoration transitions are discussed.
We propose a dispersive representation of the charged pion vector form factor that is consistent with chiral symmetry and fulfills the constraints imposed by analyticity and unitarity. Unknown ...parameters are fitted to the very precise data on
τ
−
→
π
−
π
0
ν
τ
decays obtained by Belle, leading to a good description of the corresponding spectral function up to a
ππ
squared invariant mass
s
≃1.5 GeV
2
. We determine the
ρ
(770) mass and width pole parameters and obtain the values of low-energy observables. The significance of isospin-breaking corrections is also discussed. For larger values of
s
, this representation is complemented with a phenomenological description to allow its implementation in the new TAUOLA hadronic currents.
We study the behavior of two-flavor dense quark matter under the influence of an external magnetic field in the framework of a nonlocal chiral quark model with separable interactions. The nonlocality ...is incorporated in the model by using a Gaussian form factor. It is found that for low and moderate values of magnetic field there is a decrease of the critical chiral restoration chemical potential
μ
c
, i.e. an inverse magnetic catalysis effect is observed. For larger values of
eB
the behavior of
μ
c
becomes more or less flat, depending on the parametrization. Within the considered parametrization range we do not find a significant growth of the critical chemical potential for large magnetic fields, as occurs in the case of the local NJL model.
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