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N. N. Scoccola

Publications and source records attributed to N. N. Scoccola.

At least 37 records · Page 2Linked to original sources

Towers of baryons of the ${\cal N}=2$ quark model band in the large $N_c$ limit

We performed a complete analysis of the spectrum of all the states in the ${\cal N}=2$ quark model harmonic oscillator band with $N_f=3$ in the large $N_c$ limit including the often disregarded antisymmetric multiplet $[{\bf 20},1^+]$. We included configuration mixing effects. We found that the states in the $[{\bf 56},L^+]$ and $[{\bf 70},L^+]$ with $L=0,2$ fall into nine towers of degenerate states. We found that nonstrange antisymmetric states fall into three towers and respond to the same structure as the states in the $[{\bf 70},1^-]$ multiplet. We also showed explicitly the compatibility of these results and the scattering resonance picture.

nucl-th↗

Effects of strong magnetic fields on quark matter and $π^0$ properties within nonlocal chiral quark models

We study the behavior of strongly interacting matter under a strong external magnetic field in the context of chiral quark models that include nonlocal interactions. In particular, we analyze the influence of a constant magnetic field on the chiral quark condensates at zero and finite temperature, studying the deconfinement and chiral restoration critical temperatures and discussing the observed "magnetic catalysis" and "inverse magnetic catalysis" effects. In addition, we analyze in this framework the behavior of the $π^0$ mass and decay constant. The predictions of nonlocal chiral quark models are compared with results obtained in lattice QCD.

hep-ph↗

Phase structure of magnetized 2SC quark matter under compact star conditions

Some properties of magnetized two flavor color superconducting (2SC) cold dense quark matter under compact star conditions (COSC) are investigated within a $SU(2)_f$ Nambu Jona-Lasinio type model. We study the phase diagram for several model parametrizations. The features of each phase are analyzed through the behavior of the chiral and superconducting condensates for increasing chemical potential or magnetic field. We show how the phases are modified in the presence of $β$-equilibrium as well as color and electric charge neutrality conditions.

hep-ph↗

Pion masses under intense magnetic fields within the NJL model

The behavior of charged and neutral pion masses in the presence of a static uniform magnetic field is studied in the framework of the two-flavor Nambu-Jona-Lasinio (NJL) model. Analytical calculations are carried out employing the Ritus eigenfunction method. Numerical results are obtained for definite model parameters, comparing the predictions of the model with present lattice QCD (LQCD) results.

hep-ph↗

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.

hep-ph↗

Strong magnetic fields in nonlocal chiral quark models

We study the behavior of strongly interacting matter under a uniform intense external magnetic field in the context of nonlocal extensions of the Polyakov-Nambu-Jona-Lasinio model. A detailed description of the formalism is presented, considering the cases of zero and finite temperature. In particular, we analyze the effect of the magnetic field on the chiral restoration and deconfinement transitions, which are found to occur at approximately the same critical temperatures. Our results show that these models offer a natural framework to account for the phenomenon of inverse magnetic catalysis found in lattice QCD calculations.

hep-ph↗

Neutral meson properties under an external magnetic field in nonlocal chiral quark models

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 $π^0$ and $σ$ meson masses and for the $π^0$ decay constant. Numerical results for these observables are quoted for various parameterizations. In particular, the behavior of the $π^0$ 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.

hep-ph↗

Magnetized color superconducting quark matter under compact star conditions: Phase structure within the SU(2)f NJL model

The properties of magnetized color superconducting cold dense quark matter under compact star conditions are investigated using a $SU(2)_f$ Nambu Jona-Lasinio (NJL)-type model in which the divergences are treated using a magnetic field independent regularization scheme in order to avoid unphysical oscillations. We study the phase diagram for several model parametrizations. The features of each phase are analyzed through the behavior of the chiral and superconducting condensates together with the different particle densities for increasing chemical potential or magnetic field. While confirming previous results derived for the zero magnetic field or isospin symmetric matter case, we show how the phases are modified in the presence of $β$-equilibrium as well as color and electric charge neutrality conditions.

hep-ph↗

Magnetic catalysis and inverse magnetic catalysis in nonlocal chiral quark models

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.

hep-ph↗

$η$-$γ$ and $η'$-$γ$ transition form factors in a nonlocal NJL model

We study the $η$ and $η'$ distribution amplitudes (DAs) in the context of a nonlocal SU(3)_L x SU(3)_R chiral quark model. The corresponding Lagrangian allows to reproduce the phenomenological values of pseudoscalar meson masses and decay constants, as well as the momentum dependence of the quark propagator arising from lattice calculations. It is found that the obtained DAs have two symmetric maxima, which arise from new contributions generated by the nonlocal character of the interactions. These DAs are then applied to the calculation of the $η$-$γ$ and $η'$-$γ$ transition form factors. Implications of our results regarding higher twist corrections and/or contributions to the transition form factors originated by gluon-gluon components in the $η$ and $η'$ mesons are discussed.

hep-ph↗

Vector and axial vector mesons in a nonlocal chiral quark model

Basic features of nonstrange vector and axial vector mesons are analyzed in the framework of a chiral quark model that includes nonlocal four fermion couplings. Unknown model parameters are determined from some input values of masses and decay constants, while nonlocal form factors are taken from a fit to lattice QCD results for effective quark propagators. Numerical results show a good agreement with the observed meson phenomenology.

hep-ph↗

Magnetic susceptibility of the QCD vacuum in a nonlocal SU(3) PNJL model

The magnetic susceptibility of the QCD vacuum is analyzed in the framework of a nonlocal SU(3) Polyakov-Nambu-Jona-Lasinio model. Considering two different model parametrizations, we estimate the values of the $u$ and $s$-quark tensor coefficients and magnetic susceptibilities and then we extend the analysis to finite temperature systems. Our numerical results are compared to those obtained in other theoretical approaches and in lattice QCD calculations.

hep-ph↗

BEC-BCS crossover in a cold and magnetized two color NJL model

The BEC-BCS crossover for a NJL model with diquark interactions is studied in the presence of an external magnetic field. Particular attention is paid to different regularization schemes used in the literature. A thorough comparison of results is performed for the case of a cold and magnetized two-color NJL model. According to our results, the critical chemical potential for the BEC transition exhibits a clear inverse magnetic catalysis effect for magnetic fields in the range $ 1 \lesssim eB/m_π^2 \lesssim 20 $. As for the BEC-BCS crossover, the corresponding critical chemical potential is very weakly sensitive to magnetic fields up to $eB \sim 9\ m_π^2$, showing a much smaller inverse magnetic catalysis as compared to the BEC transition, and displays a strong magnetic catalysis from this point on.

hep-ph↗

On the pentaquark candidates $P_c^+(4380)$ and $P_c^+(4450)$ within the soliton picture of baryons

Using the bound state version of the topological soliton model for the baryons we show that the existence of a bound (or quasi-bound) $\bar D$-soliton state leads to the possibility of having hidden charm pentaquarks with quantum numbers and masses, which are compatible with those of the candidates recently reported by the LHCb experiment. The implications of heavy quark symmetry are elaborated.

hep-ph↗

Inhomogeneous phases in nonlocal chiral quark models

The presence of inhomogeneous phases in the QCD phase diagram is analyzed within chiral quark models that include nonlocal interactions. We work at the mean field level, assuming that the spatial dependence of scalar and pseudo-scalar condensates is given by a dual chiral density wave. Phase diagrams for Gaussian nonlocal form factors are studied in detail and compared with those obtained within the Nambu-Jona-Lasinio model and quark-meson approaches.

hep-ph↗

Generalized Ginzburg-Landau approach to inhomogeneous phases in nonlocal chiral quark models

We analyze the presence of inhomogeneous phases in the QCD phase diagram within the framework of nonlocal chiral quark models. We concentrate in particular in the positions of the tricritical (TCP) and Lifshitz (LP) points, which are studied in a general context using a generalized Ginzburg-Landau approach. We find that for all the phenomenologically acceptable model parametrizations considered the TCP is located at a higher temperature and a lower chemical potential in comparison with the LP. Consequently, these models seem to favor a scenario in which the onset of the first order transition between homogeneous phases is not covered by an inhomogeneous, energetically favored phase.

hep-ph↗

Phase structure of cold magnetized quark matter within the SU(3) NJL model

The possible different phases of cold quark matter in the presence of a finite magnetic field and chemical potential are obtained within the SU(3) NJL model for two parameter sets often used in the literature. Although the general pattern is the same in both cases, the number of intermediate phases is parameter dependent. The chiral susceptibilities, as usually defined, are different not only for the s-quark as compared with the two light quarks, but also for the u and d-quarks, yielding non identical crossover lines for the light quark sector.

hep-ph↗

Global analysis of the negative parity non-strange baryons in the 1/Nc expansion

A global study of the negative parity non-strange baryon observables is performed in the frame- work of the 1/Nc expansion. Masses, partial decay widths and photo-couplings are simultaneously analyzed. A main objective is to determine the composition of the spin 1/2 and 3/2 nucleon states, which come in pairs and involve two mixing angles which can be determined and tested for consistency by the mentioned observables. The issue of the assignment of those nucleon states to the broken SU(4) x O(3) mixed-symmetry multiplet is studied in detail, with the conclusion that the assignment made in the old studies based on the non-relativistic quark model is the preferred one. In addition, the analysis involves an update of the input data with respect to previous works.

hep-ph↗