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V. V. Braguta

Publications and source records attributed to V. V. Braguta.

At least 55 records · Page 3Linked to original sources
arXiv2013

Electromagnetic superconductivity of vacuum induced by strong magnetic field: numerical evidence in lattice gauge theory

Using numerical simulations of quenched SU(2) gauge theory we demonstrate that an external magnetic field leads to spontaneous generation of quark condensates with quantum numbers of electrically charged rho mesons if the strength of the magnetic field exceeds the critical value eBc = 0.927(77) GeV^2 or Bc =(1.56 \pm 0.13) 10^{16} Tesla. The condensation of the charged rho mesons in strong magnetic field is a key feature of the magnetic-field-induced electromagnetic superconductivity of the vacuum.

hep-lat↗
arXiv2012

Correlations of Abelian monopoles in quark-gluon plasma

In this paper the properties of thermal Abelian monopoles in the deconfinement phase of the SU(2) gluodynamics are considered. In particular, to study the properties of the Abelian monopole component of QGP we calculate three-point correlation functions of monopoles for different temperatures from the region $T/T_c \in (1.5, 6.8)$. The results of the calculation show that the three-point correlation functions can be described by independent pair correlations of monopoles. From this one can conclude that the system of Abelian monopoles in QGP reveals the properties of a dilute gas. In addition, one can assert that the interaction between Abelian monopoles is a pair interaction and there are no three-particle forces acting between monopoles.

hep-lat↗
arXiv2012

Double charmonium production in exclusive bottomonia decays

This paper is devoted to the leading twist exclusive bottomonia decays with double charmonium in the final state. Using models of the twist-2 charmonia distribution amplitudes the widths of these decays are calculated within light cone formalism. In addition, the processes under consideration are studied within nonrelativistic QCD. In our analysis we have found that the production of some of the $P$-wave charmonia mesons with $L_z \neq 0$ is allowed already at the leading twist approximation. This means that the selection rules which predict the suppression of such decays are violated. The mechanism which lies behind this violation is discussed.

hep-ph↗
arXiv2012

Properties of the quark-antiquark-gluon Fock state in the η_c meson

In this paper the twist-3 distribution amplitude of the quark-antiquark-gluon Fock state in the η_c meson is studied. To calculate the moments of this distribution amplitude QCD sum rules is applied. Using the results of the calculation the model of this distribution amplitude is built. In addition NRQCD matrix elements which determine the properties of the quark-antiquark-gluon Fock state are determined. In particular, the probability amplitude to find the quark-antiquark pair in the color octet state, the mean gluon energy and the fraction of momentum carried by gluon, the relative velocity of the color-octet quark-antiquark-pair are calculated.

hep-ph↗
arXiv2011

Study of the thermal abelian monopoles with proper gauge fixing

The properties of the thermal abelian monopoles are studied in the deconfinement phase of the SU(2) gluodynamics. To remove effects of Gribov copies the simulated annealing algorithm is applied to fix the maximally abelian gauge. Computing the density of the thermal abelian monopoles in the temperature range between 1.5T_c and 6.9T_c we show, by comparison with earlier results, that the Gribov copies effects might be as high as 20% making proper gauge fixing mandatory. We find that in the infinite temperature limit the monopole density converges to its value in 3-dimensional theory. To study the interaction between monopoles we calculate the monopole-monopole and monopole-antimonopole correlators at different temperatures in the region (1.5T_c, 6.9T_c). Using the result of this study we determine the screening mass, monopole-monopole coupling constant, monopole size and monopole mass. In addition we check the continuum limit of our results.

hep-lat↗
arXiv2011

The Chiral Magnetic Effect and chiral symmetry breaking in SU(3) quenched lattice gauge theory

We study some properties of the non-Abelian vacuum induced by strong external magnetic field. We perform calculations in the quenched SU(3) lattice gauge theory with tadpole-improved Luscher-Weisz action and chirally invariant lattice Dirac operator. The following results are obtained: The chiral symmetry breaking is enhanced by the magnetic field. The chiral condensate depends on the strength of the applied field as a power function with exponent n = 1.6 +/- 0.2. There is a paramagnetic polarization of the vacuum. The corresponding susceptibility and other magnetic properties are calculated and compared with the theoretical estimations. There are non-zero local fluctuations of the chirality and electromagnetic current, which grow with the magnetic field strength. These fluctuations can be a manifestation of the Chiral Magnetic Effect (CME).

hep-lat↗
arXiv2011

Thermal Abelian monopoles as selfdual dyons

The properties of the thermal Abelian monopoles are studied in the deconfinement phase of the SU(2) gluodynamics. To remove effects of Gribov copies the simulated annealing algorithm is applied to fix the maximally Abelian gauge. To study monopole profile we complete the first computations of excess of the nonabelian action density as a function of the distance from the center of the thermal Abelian monopole. We have found that starting from the distances $\approx$ 2 lattice spacings the chromoelectric and chromomagnetic action densities created by monopole are equal to each other, from what we draw a conclusion that monopole is a dyon. Furthermore, we find that the chromoelectric and chromomagnetic fields decrease exponentially with increasing distance. These findings were confirmed for different temperatures in the range $T/T_c \in (1.5, 4.8)$.

hep-lat↗
arXiv2010

Exclusive C=+ charmonium production in $e^+ e^- \to H+γ$ at B-factories within light cone formalism

In this paper the cross sections of the processes $e^+ e^- \to H+γ, H=η_c, η_c', χ_{c0}, χ_{c1}, χ_{c2}$ are calculated. The calculation is carried out at the leading twist approximation of light cone formalism. Within this approach the leading logarithmic radiative and relativistic corrections to the amplitudes are resumed. For the processes $e^+ e^- \to η_c, η_c'+γ$ one loop radiative corrections are taken into account. It is also shown that one loop leading logarithmic radiative corrections calculated within light cone formalism for the processes under study coincide with that obtained by direct calculations of one loop diagrams within nonrelativistic QCD.

hep-ph↗
arXiv2009

Mass of nonrelativistic meson from leading twist distribution amplitudes

In this paper distribution amplitudes of pseudoscalar and vector nonrelativistic mesons are considered. Using equations of motion for the distribution amplitudes, it is derived relations which allow one to calculate the masses of nonrelativistic pseudoscalar and vector meson if the leading twist distribution amplitudes are known. These relations can be also rewritten as relations between the masses of nonrelativistic mesons and infinite series of QCD operators, what can be considered as an exact version of Gremm-Kapustin relation in NRQCD.

hep-ph↗
arXiv2009

Decay eta_b->J/ψJ/ψin light cone formalism

The decays of pseudoscalar bottomonium eta_b into a pair of vector charmonia, J/ψJ/ψ, J/ψψ', ψ' ψ' are considered in the light cone formalism. Relativistic and leading logarithmic radiative corrections to the amplitudes of these processes are resummed. It is shown that the small value for the branching ratio of the decay eta_b-> J/ψJ/ψobtained within the leading order nonrelativistic QCD is a consequence of a fine-tuning between certain parameters, which is broken when relativistic and leading logarithmic radiative corrections are taken into account. As a result, the branching ratio obtained in this paper is enhanced by an order of magnitude.

hep-ph↗
arXiv2009

Leading twist distribution amplitudes of P-wave nonrelativistic mesons

This paper is devoted to the study of the leading twist distribution amplitudes of P-wave nonrelativistic mesons. It is shown that at the leading order approximation in relative velocity of quark-antiquark pair inside the mesons these distribution amplitudes can be expressed through one universal function. As an example, the distribution amplitudes of the P-wave charmonia mesons are considered. Within QCD sum rules the model for the universal function of P-wave charmonia mesons is built. In addition, it is found the relations between the moments of the universal function and the nonrelativistic QCD matrix elements that control relativistic corrections to any amplitude involving P-wave charmonia. Our calculation shows that characteristic size of these corrections is of order of ~30 %.

hep-ph↗
arXiv2008

The study of double vector charmonium mesons production at B-factories within light cone formalism

In this paper the processes $e^+ e^- \to J/ΨJ/Ψ, J/Ψψ', ψ' ψ'$ are considered in the framework of light cone formalism. An important distinction of this approach in comparison to the approaches used in other papers is that relativistic and leading logarithmic radiative corrections to the cross section can be easily resummed within light cone formalism. In this paper the effect of this resummation is studied. It is shown that this effect is important especially for the production of higher charmonium mesons. The predicted cross sections are in agreement with the upper bounds set by Belle collaboration.

hep-ph↗
arXiv2008

Double charmonium production at B-factories within light cone formalism

This paper is devoted to the study of the processes e^+e^- \to J/Ψη_c, J/Ψη_c', ψ' η_c, ψ' η_c' within light cone formalism. It is shown that if one disregards the contribution of higher fock states, the twist-3 distribution amplitudes needed in the calculation can be unambiguously determined from the twist-2 distribution amplitudes and equations of motion. Using models of the twist-2 distribution amplitudes the cross sections of the processes under study have been calculated. The results of the calculation are in agreement with Belle and BaBar experiments. It is also shown that relativistic and radiative corrections to the cross sections play crucial role in the achievement of the agreement between the theory and experiments. The comparison of the results of this paper with the results obtained in other papers has been carried out. In particular, it is shown that the results of papers where relativistic and radiative corrections were calculated within NRQCD are overestimated by a factor of ~1.5.

hep-ph↗
arXiv2008

Study of exclusive processes e^+ e^- \to VP

This paper is devoted to consideration of the hard exclusive processes $e^+e^- \to VP$, where $V=ρ,ϕ; P=η,η'$. Experimental measurement of the cross section of the process $e^+ e^- \to ϕη$ at BaBar collaboration at large center mass energy $\sqrt s=10.6$ GeV and some low energy experimental data $\sqrt s \sim 2-4$ GeV give us the possibility to study the cross section in the broad energy region. As the result, we have determined the asymptotic behavior of the cross section of $e^+ e^- \to ϕη$ in the limit $s \to \infty$, which is in agreement with perturbative QCD prediction. Assuming that the same asymptotic behavior is valid for the other processes under consideration and using low energy experimental data we have predicted the cross sections of these processes at energies $\sqrt s=3.67,~10.6$ GeV. In addition, we have calculated the cross sections of these processes at the same energies within perturbative QCD. Our results are in agreement with available experimental data.

hep-ph↗
arXiv2007

The study of leading twist light cone wave functions of J/Psi meson

This paper is devoted to the study of leading twist light cone wave functions of J/Psi meson. The moments of these wave functions have been calculated within three approaches: potential models, nonrelativistic QCD and QCD sum rules. Using the results obtained within these approaches the models for the light cone wave functions of leading twist have been proposed. Similarly to the wave function of eta_c meson the leading twist light cone wave functions of J/Psi meson have very interesting properties at scales greater than m_c: improvement of the accuracy of the model, appearance of relativistic tail and violation of nonrelativistic QCD velocity scaling rules. The last two properties are the properties of true leading twist light cone wave functions of J/Psi meson.

hep-ph↗
arXiv2007

The study of leading twist light cone wave function of η_c meson

This paper is devoted to the study of leading twist light cone wave function of $η_c$ meson. The moments of this wave function have been calculated within three approaches: potential models, nonrelativistic QCD and QCD sum rules. Using the results obtained within these approaches the model for the light cone wave function of leading twist has been proposed. Being scale dependent light cone wave function has very interesting properties at scales $μ> m_c$: improvement of the accuracy of the model, appearance of relativistic tail and violation of nonrelativistic QCD velocity scaling rules. The last two properties are the properties of real leading twist light cone wave function of $η_c$ meson.

hep-ph↗
arXiv2006

The process $\epem\to J/ ψX(3940)$ at $\sqrt s = 10.6$ GeV in the framework of light cone formalism

This paper is devoted to the study of the process $\epem\to J/ψX(3940)$ in the framework of light cone formalism. In our calculation two hypotheses about the structure of X(3940) meson are considered: X(3940) is $3^1$S$_0$ state and X(3940) is one of $2^3$P states. The former hypothesis leads to a good agreements with the cross section measured at the experiment. As to the latter one, it is proposed a mechanism that allows one to understand the suppression of 2P mesons production in hard processes.

hep-ph↗