arXiv subjects

Yu. A. Simonov

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

At least 127 records · Page 7Linked to original sources

arXiv2007

Nonperturbative equation of state of quark-gluon plasma

The paper is devoted to the systematic derivation of nonperturbative thermodynamics of quark-gluon plasma, on the basis of the background perturbation theory. Vacuum background fields enter only in the form of field correlators, which are known from lattice and analytic calculations. In the lowest order in $α_s$ the purely nonperturbative $sQGP$ thermodynamics is expressed through single quark and gluon lines (single line approximation) which are interacting nonperturbatively with vacuum fields and with other lines. Nonperturbative EOS is obtained in terms (of the absolute value) of fundamental (adjoint) Polyakov loop $L_{fund(adj)}$ and spatial string tension $σ_s(T)$. In the lowest approximation the pressure for quarks (gluons) has a simple factorized form $P_{q(g)}= P_{SB} L_{fund(adj)} ,$ where $ L_i$ describe the action of vacuum colorelectric fields on particle trajectory.

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arXiv2007

Nonperturbative dynamics in the colour-magnetic QCD vacuum

In the deconfinement phase of QCD quarks and gluons interact with the dense stochastic colour-magnetic vacuum. We consider the dynamics of quarks in this deconfinement phase using the Field Correlators Method and derive an effective nonperturbative inter-quark potential, in addition to the usual perturbative short-ranged interaction. We find the resulting angular-momentum-dependent interaction to be attractive enough to maintain bound states and, for light quarks (and gluons), to cause emission of quark and gluon pairs. Possible consequences for the strong interacting quark--gluon plasma are briefly discussed.

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arXiv2007

Deconfinement transition for nonzero baryon density in the Field Correlator Method

Deconfinement phase transition due to disappearance of confining colorelectric field correlators is described using nonperturbative equation of state. The resulting transition temperature $T_c(μ)$ at any chemical potential $μ$ is expressed in terms of the change of gluonic condensate $ΔG_2$ and absolute value of Polyakov loop $L_{fund} (T_c)$, known from lattice and analytic data, and is in good agreement with lattice data for $ΔG_2 \approx 0.0035 $ GeV$^4$. E.g. $T_c(0) =0.27; 0.19; 0.17$ GeV for $n_f=0,2,3$ respectively.

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arXiv2007

Decay constants of the heavy-light mesons from the field correlator method

Meson Green's functions and decay constants $f_Γ$ in different channels $Γ$ are calculated using the Field Correlator Method. Both, spectrum and $f_Γ$, appear to be expressed only through universal constants: the string tension $σ$, $α_s$, and the pole quark masses. For the $S$-wave states the calculated masses agree with the experimental numbers within $\pm 5$ MeV. For the $D$ and $D_s$ mesons the values of $f_{\rm P} (1S)$ are equal to 210(10) and 260(10) MeV, respectively, and their ratio $f_{D_s}/f_D$=1.24(3) agrees with recent CLEO experiment. The values $f_{\rm P}(1S)=182, 216, 438$ MeV are obtained for the $B$, $B_s$, and $B_c$ mesons with the ratio $f_{B_s}/f_B$=1.19(2) and $f_D/f_B$=1.14(2). The decay constants $f_{\rm P}(2S)$ for the first radial excitations as well as the decay constants $f_{\rm V}(1S)$ in the vector channel are also calculated. The difference of about 20% between $f_{D_s}$ and $f_D$, $f_{B_s}$ and $f_B$ directly follows from our analytical formulas.

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arXiv2006

Masses and decay constants of B_q mesons in the QCD string approach

The relativistic string Hamiltonian is used to calculate the masses and decay constants of $B_q$ mesons: they appear to be expressed through onlythree fundamental values: the string tension $σ$, $α_s$, and the quark pole masses. The values $f_B =186 $ MeV, $f_{B_s}= 222$ MeV are calculated while $f_{B_c}$ depends on the $c$-quark pole mass used, namely $f_{B_c}=440 (424)$ MeV for $m_c =1.40 (1.35)$ GeV. For the $1P$ states we predict the spin-averaged masses: $\bar M(B_J)=5730$ MeV and $\bar M(B_{sJ})=5830$ MeV which are in good agreement with the recent data of the D0 and CDF Collaborations, at the same time owning to the string correction being by $\sim 50$ MeV smaller than in other calculations.

hep-ph↗

arXiv2006

Nucleon matrix elements and baryon masses in the Dirac orbital model

Using the expansion of the baryon wave function in a series of products of single quark bispinors (Dirac orbitals), the nonsinglet axial and tensor charges of a nucleon are calculated. The leading term yields $g_A = 1.27$ in good agreement with experiment. Calculation is essentially parameter-free and depends only on the strong coupling constant value $α_s$. The importance of lower Dirac bispinor component, yielding 18% to the wave function normalization is stressed. As a check, the baryon decuplet masses in the formalism of this model are also computed using standard values of the string tension $σ$ and the strange quark mass $m_s$; the results being in a good agreement with experiment.

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arXiv2006

New nonperturbative approach to the Debye mass in hot QCD

The Debye mass m_D is computed nonperturbatively in the deconfined phase of QCD, where chromomagnetic confinement is known to be present. The latter defines m_D to be m_D=c_D\sqrt{σ_s}, where c_D \cong 2.06 and σ_s=σ_s(T) is the spatial string tension. The resulting magnitude of m_D(T) and temperature dependence are in good agreement with lattice calculations. Background perturbation theory expansion for m_D(T) is discussed in comparison to standard perturbative results and recent gauge-invariant definitions.

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arXiv2006

Confinement of light quarks in QCD at finite density

The 4q effective Lagrangian and the gap equation are derived for light quarks in the confinement phase of QCD. The modification of the confining string due to finite quark density (chemical quark potential μ) is observed. As a surprising result in a multiquark system with a common string junction an attractive well appears of radius μ/σand of an average depth equal to μ. Possible implications for the density phase transition are discussed.

hep-ph↗

arXiv2006

Odderon and Pomeron from the Vacuum Correlator Method

Glueball masses with J<=7 are computed both for C=+1 and C=-1 using the string Hamiltonian derived in the framework of the Vacuum Correlator Method. No fitting parameters are used, and masses are expressed in terms of string tension $σ$ and effective value of $α_s$. We extend the calculations done for J<=3 using the same Hamiltonian, which provided glueball masses in good agreement with existing lattice data, to higher mass states. It is shown that 3^{--}, 5^{--} and 7^{--} states lie on the odderon trajectories with the intercept around or below 0.14. Another odderon trajectory with 3g glueballs of Y-shape, corresponds to 11% higher masses and low intercept. These findings are in agreement with recent experimental data, setting limits on the odderon contribution to the exclusive $γp$ reactions.

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arXiv2006

Glueballs, gluerings and gluestars in the d=2+1 SU(N) gauge theory

The 3d gluodynamics which governs the large T quark gluon plasma is studied in the framework of the field correlator method. Field correlators and spacial string tension are derived through the gluelump Green's functions. The glueball spectrum is calculated both in C=-1 as well as in C=+1 sectors, and multigluon bound states in the form of "gluon rings" and "gluon stars" are computed explicitly. Good overall agreement with available lattice data is observed.

hep-ph↗

arXiv2005

Dynamics of quark-gluon plasma from Field correlators

It is argued that strong dynamics in the quark-gluon plasma and bound states of quarks and gluons is mostly due to nonperturbative effects described by field correlators. The emphasis in the paper is made on two explicit calculations of these effects from the first principles: one analytic using gluelump Green's functions and another using independent lattice data on correlators. The resulting hadron spectra are investigated in the range T_c < T < 2T_c. The spectra of charmonia, bottomonia, light s-sbar mesons, glueballs and quark-gluon states calculated numerically are in general agreement with lattice MEM data. The possible role of these bound states in the thermodynamics of quark-gluon plasma is discussed.

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arXiv2005

Spin-dependent interaction in the deconfined phase of QCD

Spin-dependent deconfined interaction in the Q\barQ system is derived from the field correlators known from lattice and analytic calculations. As a result hyperfine splitting is found numerically for charmonium, bottomonium and strangeonium in the range T_c<T<2T_c. Spin-orbit interaction due to magnetic correlators (the Thomas term) is able to produce numerous Q\barQ bound states with accumulation point at M=m_Q+m_\barQ. Possible influence of these effects on the thermodynamics of quark-gluon plasma is discussed.

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arXiv2005

Pentaquarks in the Jaffe-Wilczek approximation

The masses of $uudd\bar s $, $uudd\bar d$ and $uuss\bar d$ pentaquarks are evaluated in a framework of both the Effective Hamiltonian approach to QCD and spinless Salpeter using the Jaffe--Wilczek diquark approximation and the string interaction for the diquark--diquark--antiquark system. The pentaquark masses are found to be in the region above 2 GeV. That indicates that the Goldstone boson exchange effects may play an important role in the light pentaquarks. The same calculations yield the mass of $[ud]^2\bar c$ pentaquark $\sim$ 3250 MeV and $[ud]^2\bar b$ pentaquark $\sim$ 6509 MeV.

hep-ph↗

arXiv2005

QCD string and the Lorentz nature of confinement

We address the question of the Lorentz nature of the effective long-range interquark interaction generated by the QCD string with quarks at the ends. Studying the Dyson-Schwinger equation for a heavy-light quark-antiquark system, we demonstrate explicitly how a Lorentz-scalar interaction appears in the Diraclike equation for the light quark, as a consequence of chiral symmetry breaking. We argue that the effective interquark interaction in the Hamiltonian of the QCD string with quarks at the ends stems from this effective scalar interaction.

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arXiv2005

Axial and tensor charge of the nucleon in the Dirac orbital model

Using the expansion of the baryon wave function in a series of products of single quark bispinors (Dirac orbitals), the nonsinglet axial and tensor charge of the nucleon are calculated. The leading term yields ${G_A}/{G_V} = 1.27$ and in good agreement with experiment. Calculation is essentially parameter-free and depends on the string tension $σ$ and $α_s$, fixed at standard values. The importance of lower Dirac bispinor component, yielding 18% to the wave function normalization is stressed.

hep-ph↗

arXiv2005

Strong interaction and bound states in the deconfinement phase of QCD

Recent striking lattice results on strong interaction and bound states above T_c can be explained by the nonperturbative Q\bar Q potential, predicted more than a decade ago in the framework of the field correlator method. Explicit expressions and quantitative estimates are given for Polyakov loop correlators in comparison with lattice data. New theoretical predictions for glueballs and baryons above T_c are given.

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arXiv2005

Analytic calculation of field-strength correlators

Field correlators are expressed using background field formalism through the gluelump Green's functions. The latter are obtained in the path integral and Hamiltonian formalism. As a result behaviour of field correlators is obtained at small and large distances both for perturbative and nonperturbative parts. The latter decay exponentially at large distances and are finite at x=0, in agreement with OPE and lattice data.

hep-ph↗

arXiv2004

Pentaquarks in string dynamics

The masses of $uudd\bar s $, $uudd\bar d$, and $uuss\bar d$ pentaquarks are evaluated in a framework of both the Effective Hamiltonian approach to QCD and spinless Salpeter using the Jaffe-Wilczek diquark approximation and the string interaction for the diquark-diquark-antiquark system. The masses of the light pentaquarks are found to be in the region above 2 GeV. The similar calculations yield the mass of $[ud]^2\bar c$ pentaquark $\sim$ 3250 MeV and $[ud]^2\bar b$ pentaquark $\sim$ 6509 MeV.

hep-ph↗