arXiv subjects

Yu. A. Simonov

Publications and source records attributed to Yu. A. Simonov.

At least 37 records · Page 2Linked to original sources

arXiv2020

The Relativistic Cornell-type Mechanism of Exotic Scalar Resonances

The formalism of the coupled $q\bar q$ and the $φφ( π-π$, $K\bar K, πK,...$) scalar channels is formulated, taking into account the ground and radial excited $q\bar q$ poles. The basic role is shown to be played by the transition coefficients $k^{(I)} (q\bar q, |φφ)$, which are calculated using the quark-chiral Lagrangian without free parameters. The resulting method, called the pole projection mechanism (PPM), ensures: 1) one resonance for each $φφ$ channel from the basic $q\bar q$ pole, e.g. the $f_0 (500)$ resonance in the $ππ$ channel; 2) a possibility to have two $φφ$ resonances, coupled to the same $q\bar q$ state, when the channel coupling is taken into account in the meson-meson channels, which yields $f_0 (500)$ and $f_0(980)$ from the same $n\bar n$ pole around 1 GeV; 3) the strong pole shift down for special ($ππ, πK)$ channels due to large transition coefficients $k^{(I)}$, computed in this formalism without free parameters. The parameters of calculated complex poles are in reasonable agreement with the experimental data of the resonances $f_0(500)$, $f_0(980)$, $a_0(980)$, $a_0(1450)$, $K^*_0(700)$, $K^*_0(1430)$, $f_0(1370)$ and $f_0(1710)$.

hep-ph↗

arXiv2020

Hadron Form Factors with the Boost-Corrected Wave Functions

Hadron form factors are calculated using the Lorentz contracted wave functions, determined in the arbitrary dynamical scheme with the instantaneous interaction. It is shown that the large $Q$ asymptotics of the form factors is defined by the contraction coefficient $C_m(Q^2) = \frac{m}{\sqrt(m^2+ Q^2/4)}$, where $m$ is the meson mass, and weakly depends on the interaction used. The resulting form factors $F_π$ and $F_K$ are obtained in good agreement with the lattice and experimental data. Important consequences for the dynamics of hadron decays and scattering are shortly discussed.

hep-ph↗

arXiv2020

Scalar mesons in the chiral theory with quark degrees of freedom

The Chiral Confining Lagrangian, based on the chiral theory with quark degrees of freedom, is used to study the spectroscopy of scalar mesons. The formalism does not contain arbitrary fitting parameters and takes into account infinite number of transitions from meson-meson to quark-antiquark states. Starting from known $q\bar q$ poles the transition coefficients ensure the strong shift of the poles for the $ππ$ and much smaller shift for the $K\bar K$ systems. The resulting amplitudes $f_{ππ}$ and $f_{K\bar K}$ are calculated in terms of the $q\bar q$ and the free meson Green's functions. With the account of the $ππ/K\bar{K}$ channel coupling one obtains two resonances: a wide resonance $E_1$ in the range 500-700 MeV and narrow $E_2 $ near 1 GeV, which can be associated with $f_0(500)$ and $f_0(980)$. A similar analysis, applied to the $I=1$ channel, shows that in this case two very close poles in different sheets appear near $E=980$ MeV, which can be associated with the $a_0 (980)$ resonance. The obtained $ππ$ interaction amplitudes, $\operatorname{Re} f_{ππ} (E)$ and $\operatorname{Im} f_{ππ}(E)$ are compared with the known data.

hep-ph↗

arXiv2019

Thermodynamics of quark-gluon plasma at finite baryon density

Properties of the quark-gluon plasma(QGP) in the presence of the baryon chemical potential $μ_B$ are studied using the Field Correlator Method(FCM). The nonperturbative FCM dynamics includes the Polyakov line, computed via colorelectric string tension $σ^E(T)$ and the quark and gluon Debye masses, defined by the colormagnetic string tension $σ^H(T)$. The resulting QGP thermodynamics at $μ_B \le 400$ MeV is in a good agreement with the available lattice data,both pressure and the sound velocity do not show any sign of a critical behavior in this region.

hep-ph↗

arXiv2019

Dense Quark-Gluon Plasma in strong magnetic fields

A non-perturbative (np) method of Field Correlators (FCM) was applied to study QCD at temperatures above the deconfinement transition ($1<T/T_c<3,~T_c\sim0.16~GeV$) and nonzero baryon densities (baryon chemical potential $μ_B<0.5~GeV$) in an external uniform magnetic field ($eB<0.5~GeV^2$). Within FCM, the np high-temperature dynamics is embodied in the Polyakov loop and in the Debye mass due to the Color-Magnetic Confinement. Analytic expressions for quark pressure and magnetic susceptibility were obtained. The expressions were represented as series and in integral form. Magnetic susceptibility was found to increase rapidly with temperature and slowly with density. The results at the zero density limit are in agreement with lattice data.

hep-ph↗

arXiv2019

Dynamics of the Polyakov loops in QCD

A non-perturbative method of Field Correlators is applied to calculate the Polyakov loop dependence on temperature, $L(T)$, in the 2+1 flavor QCD with small quark masses, so the only relevant scale is the color-electric string tension $σ(T)$. Polyakov loop in the temperature range 100 MeV $\lesssim T\lesssim$ 400 MeV is expressed via the heavy-light meson mass that decreases with $T$ as $\sqrt{σ(T)}$. The latter is deduced from a gradually vanishing chiral condensate. The resulting $L(T)$ is in good agreement with recent lattice data.

hep-ph↗

arXiv2019

Exact relativistic Green's functions for the time-independent potentials

Relativistic formalism of Green's functions is dicussed in QCD and QED,where the relativistic Green's functions are constructed using the Schwinger proper time formalism and the Fock-Feynman-Schwinger method.As a result a simple and exact method is found for the relativistic systems,where the interaction can be written in a time-independent form.In this case one can write the relativistic Green's function as a one-dimensional integral of the corresponding nonrelativistic Green's function.The explicit example for the problem of a charge in the constant magnetic field is discussed in detail,and the exact agreement with the Schwinger relativistic form is demonstrated. A similar analysis is performed in the relativistiv Coulomb probem,supporting the accuracy of the proposed relativistic formalism.

hep-ph↗

arXiv2019

Field Correlator Method for the confinement in QCD

The theory of confinement based on the stochastic field mechanism, known as the Field Corrleator Method (FCM) is discussed in detail. Experimental and lattice data have accumulated a vast amount of material on the properties of confinement in QCD. We enumerateall these properties as 1)-7), and discuss beyond FCM two existing approaches: monopole based Dual Ginzburg-Landau (DGL) theory,and Gribov-Zwanziger model, from this point of view. It is shown that the FCM satisfies all required criteria. We also prove its selfconsistency; in particular, it is shown that the string tension σ is the only scaleful parameter in the theory beyond fermion masses, and Λ_QCD is calculated explicitly to the lowest order in terms of σ. We also formulate physical consequences of confinement, such as string breaking,Regge trajectories, role of confinement in the perturbation theory, chiral symmetry breaking, confinement in the boosted systems etc. It is demonstrated that the FCM is a suitable tool for the solution of these problems.

hep-ph↗

arXiv2019

Speed of sound, breaking of conformal limit and instabilities in quark-gluon plasma at finite baryon density

The properties of the quark-gluon plasma(QGP) in the presence of baryon chemical potential are studied using the Field Correlator Method(FCM). At low densities the QGP thermodynamics with the colormagnetic confinement and the Polyakov line interaction is in good agreement with lattice data,and the speed of sound satisfies $C_s^2\leq \frac13$,but in the intermediate range of densities the speed of sound displays a singular behaviour and one needs density modifications of the Polyakov line interaction to avoid instabilities. In particular for $μ_q >0.5$ GeV there exists a region in the $(μ, T)$ plane where $C^2_s$ violates the conformal limit. This behaviour is strongly connected to the properties of the Polyakov loop and its density dependence.

hep-ph↗

arXiv2018

The speed of sound in QGP and SU(3) Yang-Mills theory

The speed of sound $C_{s}$ in the SU(3) and (2+1)QCD is calculated within the Field Correlator Method using the nonperturbative colour magnetic confinement and Polyakov loop interaction in the deconfined region.The resulting $C_{s}$ displays a discontinuity at $T=T_{c}$ in the SU(3) case. It is shown numerically and analytically that $ C^{2}_{s}$ never exceeds $\frac{1}{3}$ both for SU(3) and (2+1) QCD for vanishing chemical potential.A good agreement is found of our numerical results with the corresponding lattice data.

hep-ph↗

arXiv2018

Chiral physics in the magnetic field with quark confinement contribution

The standard chiral perturbation theory is known to predict much weaker effects in magnetic field, than found in numerical lattice data. To overcome this disagreement we are using the effective chiral confinement Lagrangian, $L_{ECCL}$, containing both chiral and quark degrees of freedom, in the presence of external magnetic field. Without magnetic fields $L_{ECCL}$ reduces to the ordinary chiral Lagrangian $L_{EC L}$, yielding in the lowest order $O(\partial_μφ)^2$ all known relations, and providing explicit numerical coefficients in the higher $O(p^4, p^6)$ orders. The inclusion of the magnetic field in $L_{ECCL}$ strongly modifies ECL results for chiral condensates, coupling constants $f_π, f_K$ and masses of chiral mesons. The resulting behavior contains the only parameter -- the string tension $σ$, is roughly proportional to $O\left( \frac{eB}σ\right)$ and agrees very well with lattice data. These results show that the magnetic field acts not only on the chiral degrees of freedom $(φ_π)$, but also on quarks in the quark-chiral Lagrangian, which produce much stronger effect.

hep-ph↗

arXiv2018

Fractional dynamics of fermion generations

The dynamics of fermion generations is treated in the framework of the fractional Lagrangian and Hamiltonian in the compact extra dimension. The resulting spectra for u, d, e generations are described by the only mass parameter and slightly different fractional numbers, while the neutrino spectra need another mass parameter and a single fractional number for all neutrino species. New definitions of CKM and PMNS mixing matrices with standard data are given as the interference integrals in the extra dimension. A possibility of higher fermion states as dark matter candidates is shortly discussed.

hep-ph↗

arXiv2017

Nonperturbative QCD thermodynamics in the external magnetic field

The thermodynamics of quarks and gluons strongly depends on the vacuum colormagnetic field, which grows with the temperature $T$, so that spatial string tension $σ_s ={\rm const}~ g^4 (T) T^2$. We investigate below what happens when one imposes in addition constant magnetic field and discover remarkable structure of the resulting thermodynamic potential.

hep-ph↗

arXiv2017

Nonperturbative quark-gluon thermodynamics at finite density

Thermodynamics of the quark-gluon plasma at finite density is studied in the framework of the Field Correlator Method, where thermodynamical effects of Polyakov loops and colormagnetic confinement are taken into account. Having found good agreement with numerical lattice data for zero density, we calculate pressure $P(T,\,μ)$ for $0 <μ< 400$ MeV and $150 <T< 1000$ MeV. For the first time the explicit intergral form is found in this region,demonstrating analytic structure in the complex $μ$ plane. The resulting multiple complex branch points are found at the Roberge-Weiss values of $\operatorname{Im}\,μ$, with $\operatorname{Re}\,μ$ defined by the values of Polyakov lines and colormagnetic confinement.

hep-ph↗

arXiv2017

Color screening in flux tubes and in the color Coulomb potential from the QCD Field Correlators

Colorelectric and Colormagnetic structure of the flux tubes, connecting heavy quark and antiquark, is investigated in the framework of the Field Correlator method which describes all resulting fields in terms of correlators $D^E$ and $D^E_1$. The latter have been computed via gluelumps, which allows to predict the resulting distribution of color fields $\mathbf{E} (\mathbf{r}),$ and colormagnetic currents $\mathbf{k} (\mathbf{r})$ in the flux tubes. It is shown, that at large distances $r\gg λ\approx 0.2$ fm the whole structure of fields and relations between them is similar to that of the dual superconductor theory, but the basic dynamics, including small distances, is given by field correlators of the real stochastic vacuum. The important contradiction between the strong screening of color fields in the width of flux tubes and almost no screening in the perturbative $Q\bar Q$ potential is resolved.

hep-ph↗

arXiv2017

Magnetic confinement and the Linde problem

Perturbation theory of thermodynamic potentials in QCD at $T>T_c$ is considered with the nonperturbative background vacuum taken into account. It is shown that the magnetic confinement in the QCD vacuum prevents the infrared catastrophe of the perturbation theory present in the case of the free vacuum (the "Linde problem"). A short discussion is given of the applicability of the nonperturbative formalism at large $T$ and of the relation with the HTL theory.The observation of A.D.Linde, that the terms $O(g^n), n>6$ contribute to the order $O(g^6)$ is confirmed also with the account of the colormagnetic confinement, and it is shown that the latter makes these terms IR convergent, and summable. As a result one obtains the selfconsistent theory of the gluon plasma.

hep-ph↗

arXiv2017

The Evolution of Meson Masses in a Strong Magnetic Field

Spectra of $q \bar{q}$ hadrons are investigated in the framework of the Hamiltonian obtained from the relativistic path integral in external homogeneous magnetic field. The spectra of all 12 spin-isospin s-wave states, generated by $π$ and $ρ$ mesons with different spin projections, are studied both analytically and numerically on the lattice as functions of (magnetic field) $eB$. Results are in agreement and demonstrate three types of behavior, with characteristic splittings predicted by the theory.

hep-ph↗

arXiv2017

Colormagnetic confinement in the quark-gluon thermodynamics

Nonperturbative effects in the quark-gluon thermodynamics are studied in the framework of Vacuum Correlator Method. It is shown, that two correlators: colorelectric $D_1^E(x)$ and colormagnetic $D^H(x)$, provide the Polyakov line and the colormagnetic confinement in the spatial planes respectively. As a result both effects produce the realistic behavior of $P(T)$ and $s(T)$, being in good agreement with numerical lattice data.

hep-ph↗