arXiv subjects

Yu. L. Kalinovsky

Publications and source records attributed to Yu. L. Kalinovsky.

At least 37 records · Page 2Linked to original sources

arXiv2005

Effects of the restoration of U$_A$(1) symmetry on pseudoscalar meson observables

We investigate the restoration of chiral SU$(3)\otimes$SU$(3)$ and axial U$_A$(1) symmetries, at finite temperature and density, in the framework of the three flavor Nambu-Jona-Lasinio model with anomaly. We implement a temperature (density) dependence of the anomaly coefficient motivated by lattice results for the topological susceptibility and we discuss the restoration of symmetries by analyzing the behavior of the mesonic chiral partners and of the mixing angles. The results indicate that the axial part of the symmetry is restored before the possible restoration of the full U(3)$\otimes$U(3) chiral symmetry can occur.

hep-ph↗

arXiv2005

New contributions to heavy-quarkonium production

We reconsider quarkonium production in a field-theoretical setting and we show that the lowest-order mechanism for heavy-quarkonium production receives in general contributions from two different cuts. The first one corresponds to the usual colour-singlet mechanism. The second one has not been considered so far. We treat it in a gauge-invariant manner, and introduce new 4-point vertices, suggestive of the colour-octet mechanism. These new objects enable us to go beyond the static approximation. We show that the contribution of the new cut can be as large as the usual colour-singlet mechanism at high transverse momentum for J/psi. In the psi' case, theoretical uncertainties are shown to be large and agreement with data is possible.

hep-ph↗

arXiv2005

Scalar sigma meson at finite temperature in nonlocal quark model

Properties and temperature behavior of pi and sigma bound states are studied in the framework of the nonlocal model with a separable interaction kernel based on the quark Dyson-Schwinger and the meson Bethe-Salpeter equations. M_pi(T), f_pi(T), M_sigma(T) and Gamma_{sigma -> pi pi}(T) are considered above and below the deconfinement and chiral restoration transitions.

hep-ph↗

arXiv2005

Analysis of U$_A$(1) symmetry-breaking and restoration effects on the scalar-pseudoscalar spectrum

We explore patterns of effective restoration of the chiral U$_A$(1) symmetry using an extended three-flavor Nambu-Jona-Lasinio model that incorporates explicitly the axial anomaly through the 't Hooft interaction, and assuming that the coefficient of the anomaly term is temperature and density dependent. The special case of explicit breaking of chiral symmetry without U$_A$(1) anomaly is also considered, since this scenario can provide additional information allowing to understand the interplay between the U$_A$(1) anomaly and (spontaneous) chiral symmetry breaking effects. The pseudoscalar and scalar sectors are analyzed in detail bearing in mind the identification of chiral partners and the study of its convergence. We also concentrate on the behavior of the mixing angles that give us relevant information on the issue under discussion. In the region of temperatures (densities) studied, we do not observe signs indicating a full restoration of U(3)$\otimes$U(3) symmetry as, for instance, the degeneracy of both $a_0$ and $f_0$ mesons with the pion. As we work in a real world scenario ($m_u=m_d<<m_s$), we only observe the return to symmetries of the classical QCD Lagrangian in the non-strange sector.

hep-ph↗

arXiv2005

Restoration of U$_A$(1) symmetry and meson spectrum in hot or dense matter

We explore the effects of breaking and restoration of chiral and axial symmetries using an extended three-flavor Nambu-Jona-Lasinio model that incorporates explicitly the axial anomaly through the 't Hooft interaction. We implement a temperature (density) dependence of the anomaly coefficient motivated by lattice results for the topological susceptibility. The spectrum of scalar and pseudoscalar mesons is analyzed bearing in mind the identification of chiral partners and the study of its convergence. We also concentrate on the behavior of the mixing angles that give us relevant information on the issue under discussion. The results suggest that the axial part of the symmetry is restored before the possible restoration of the full U(3)$\otimes$U(3) chiral symmetry might occur.

hep-ph↗

arXiv2004

Effective restoration of the U_A(1) symmetry with temperature and density

We investigate the full U(3)$\otimes$U(3) chiral symmetry restoration, at finite temperature and density, on the basis of a quark model which incorporates the most relevant properties of QCD in this context: explicit and spontaneous breaking of chiral symmetry and axial U$_A$(1) symmetry breaking. A specific lattice-inspired behavior of the topological susceptibility, combined with the convergence of chiral partners, signals the onset of an effective chiral symmetry restoration. The results suggest that the axial part of the symmetry is restored before the possible restoration of the full U(3)$\otimes$U(3) chiral symmetry can occur. This conclusion is valid in the context of both finite temperature and density.

hep-ph↗

arXiv2004

Phase transitions and behavior of kaons in hot and dense matter

We study phase transitions and the behavior of kaons in hot and dense matter, giving special attention to the role of strange quarks. At T=0, it is found that the fraction of the strange valence quarks affects the energy per particle of the system, without changing the nature of the phase transition, and, on the other side, it has meaningful effects on the behavior of kaons and antikaons masses. The phase behavior of kaons in the $T-ρ$ plane is analyzed in connection with the chiral phase transition.

hep-ph↗

arXiv2004

Is the U$_A$(1) symmetry restored at finite temperature or density?

We investigate the full U(3)$\otimes$U(3) chiral symmetry restoration, at finite temperature and density, on the basis of the three flavor Nambu-Jona-Lasinio model with the anomaly term given by the 't Hooft interaction. We implement a temperature (density) dependence of the anomaly coefficient motivated by lattice results for the topological susceptibility. The results suggest that the axial part of the symmetry is restored before the possible restoration of the full U(3)$\otimes$U(3) chiral symmetry can occur.

hep-ph↗

arXiv2004

Effective restoration of chiral and axial symmetries at finite temperature and density

The effective restoration of chiral and axial symmetries is investigated within the framework of the SU(3) Nambu-Jona-Lasinio model. The topological susceptibility, modeled from lattice data at finite temperature, is used to extract the temperature dependence of the coupling strength of the anomaly. The study of the scalar and pseudoscalar mixing angles is performed in order to discuss the evolution of the flavor combinations of $q \bar q$ pairs and its consequences for the degeneracy of chiral partners. A similar study at zero temperature and finite density is also realized.

hep-ph↗

arXiv2004

Two photon decay of $π^0$ and $η$ at finite temperature and density

A comparative study of the anomalous decays $π^0, η\toγγ$, at finite temperature and at finite density, is performed in the framework of the three--flavor Nambu--Jona-Lasinio. The similarities and differences between both scenarios are discussed. In both cases the lifetimes of these mesons decrease significantly at the critical point, although this might not be sufficient to observe enhancement of these decays in heavy-ion collisions.

hep-ph↗

arXiv2004

Anomalous decay of pion and eta at finite temperature

We study the anomalous decays $π^0, η\toγγ$ in the framework of the three--flavor Nambu--Jona-Lasinio [NJL] model at finite temperature. The similarities and differences between these results and those obtained at zero temperature and finite density are discussed. In both cases the lifetimes of these mesons decrease significantly at the critical point, although this might not be sufficient to observe enhancement of these decays in heavy-ion collisions.

hep-ph↗

arXiv2004

Pseudoscalars Mesons in Hot, Dense Matter

Phase transitions in hot and dense matter and the in--medium behavior of pseudoscalar mesons ($π^{\pm}, π^0, K^{\pm}, K^0 ,\bar K^0,η{and} η' $) are investigated, in the framework of the three flavor Nambu--Jona-Lasinio model, including the 't Hooft interaction, which breaks the $U_A(1)$ symmetry. Three different scenarios are considered: zero density and finite temperature, zero temperature and finite density in quark matter with different degrees of strangeness, and finite temperature and density. At T=0, the role of strange valence quarks in the medium is discussed, in connection with the phase transition and the mesonic behavior. It is found that the appearance of strange quarks, above certain densities, leads to meaningful changes in different observables, especially in matter with β$ --equilibrium. The behavior of mesons in the $T-ρ$ plane is analyzed in connection with possible signatures of restoration of symmetries.

hep-ph↗

arXiv2004

Charged pions and kaons weak leptonic decays at finite density

The weak leptonic decays $π^\pm\toμ^\pmν_μ(\barν_μ), π^\pm\to e^\pmν_e(\barν_{e}), K^\pm\toμ^\pmν_μ(\barν_μ)$ and $K^\pm\to e^\pm ν_e(\barν_{e})$ are investigated within the framework of the SU(3) Nambu-Jona-Lasinio model, in the vacuum and in quark matter in $β$ equilibrium. It is found that, at low densities, the decay rates of the charge multiplets, that are decoupled in this kind of flavor asymmetric matter, are affected differently. As the density increases, these decay rates become closer and show a tendency to vanish. This shows that weak interactions are strongly influenced by the medium as a consequence of restoration of chiral symmetry.

hep-ph↗

arXiv2003

Anomalous decay of pion and eta at finite density

We study the anomalous decays $π^0, η\toγγ$ in the framework of the three--flavor Nambu--Jona-Lasinio [NJL] model, in the vacuum and in quark matter in $β$ --equilibrium. It is found that the behavior of the relevant observables essentially reflects a manifestation of the partial restoration of chiral symmetry, in non strange and strange sectors. The probability of such decays decreases with density, showing that anomalous mesonic interactions are significantly affected by the medium.

hep-ph↗

arXiv2003

$η- η'$ in a hot and dense medium

The behavior of $η$ and $η'$ in hot strange quark matter in weak equilibrium with temperature, is investigated within the SU(3) Nambu-Jona-Lasinio [NJL] model. Possible manifestations of restoration of symmetries, by temperature or density, in the behavior of $η$ and $η'$ are discussed. The role played by the combined effect of temperature and density in the nature of the phase transition and meson behavior is also analyzed.

hep-ph↗

arXiv2003

Pseudoscalar neutral mesons in hot and dense matter

The behavior of neutral pseudoscalar mesons $π^0, η$ and $η'$ in hot and dense matter is investigated, in the framework of the three flavor Nambu-Jona-Lasinio model. Three different scenarios are considered: zero density and finite temperature, zero temperature and finite density in a flavor asymmetric medium with and without strange valence quarks, and finite temperature and density. The behavior of mesons is analyzed in connection with possible signatures of restoration of symmetries. In the high density region and at zero temperature it is found that the mass of the $η'$ increases, the deviation from the mass of the $η$ being more pronounced in matter without strange valence quarks.

hep-ph↗

arXiv2001

Finite T meson correlations and quark deconfinement

Finite temperature spatial $\bar q q$ correlation modes in the $π$ and $ρ$ channels are studied with the rainbow-ladder truncated quark Dyson-Schwinger equation and Bethe-Salpeter equation in the Matsubara formalism. To retain the finite range of the effective interaction while facilitating summation over fermion Matsubara modes necessary to ensure continuity at {T=0}, a separable kernel is used. The model is fixed by {T=0} properties and it implements dynamical chiral symmetry breaking and quark confinement. Above and below the deconfinement and chiral restoration transitions, we study $M_π(T)$, $f_π(T)$ and the 3-space transverse and longitudinal masses $M_ρ^T(T)$ and $M_ρ^L(T)$. For the $ρ$ mode we also study the strong and electromagnetic partial widths to determine the $T$-dependence that is generated by the quark content. The $ρ\to ππ$ width decreases sharply just above the chiral restoration transition leaving the $ρ$ with only its narrow {$e^+ e^-$} width. We discuss improvements needed by this model, especially in regard to the high $T$ behavior of the masses where we compare to lattice QCD simulations.

nucl-th↗

arXiv2000

Mott dissociation of D-mesons at the chiral phase transition and anomalous J/Psi suppression

We investigate the in-medium modification of the charmonium breakup processes due to the Mott-effect for D-mesons at the chiral phase transition. A model calculation for the process J/Psi+pi --> D+D^*+ h.c. is presented which demonstrates that threshold effects in the thermal averaged breakup cross section can be explained as a Mott transition where final state quark-antiquark bound states enter the continuum of resonant states at the QCD phase transition. Applications to heavy-ion collisions within a modified Glauber model scenario and the phenomenon of anomalous J/$ψ$ suppression in the CERN NA50 experiment are addressed.

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