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D. Ebert

Publications and source records attributed to D. Ebert.

At least 91 records · Page 5Linked to original sources
arXiv2002

Radiative M1-decays of heavy-light mesons in the relativistic quark model

Radiative magnetic dipole decays of heavy-light vector mesons into pseudoscalar mesons V -> Pγare considered within the relativistic quark model. The light quark is treated completely relativistically, while for the heavy quark the 1/m_Q expansion is used. It is found that relativistic effects result in a significant reduction of decay rates. Comparison with previous predictions and recent experimental data is presented.

hep-ph↗
arXiv2002

Decay constants of heavy-light mesons in the relativistic quark model

The decay constants of pseudoscalar and vector heavy-light mesons are calculated in the framework of the relativistic quark model with the completely relativistic treatment of the light quark. It is argued that relativistic effects play a significant role. Good agreement of the model predictions with recent lattice and QCD sum rule calculations as well as available experimental data is found.

hep-ph↗
arXiv2002

Mass spectra of doubly heavy baryons in the relativistic quark model

Mass spectra of baryons consisting of two heavy (b or c) and one light quarks are calculated in the framework of the relativistic quark model. The light quark-heavy diquark structure of the baryon is assumed. Under this assumption the ground and excited states of both the diquark and quark-diquark bound system are considered. The quark-diquark potential is constructed. The light quark is treated completely relativistically, while the expansion in the inverse heavy quark mass is used revealing the close similarity with the mass spectra of B and D mesons. We find that the relativistic treatment of the light quark plays an important role. The level inversion of the p-wave excitations of the light quark in doubly heavy baryons is discussed.

hep-ph↗
arXiv2001

The Influence of an External Chromomagnetic Field on Color Superconductivity

We study the competition of quark-antiquark and diquark condensates under the influence of an external chromomagnetic field modelling the gluon condensate and in dependence on the chemical potential and temperature. As our results indicate, an external chromomagnetic field might produce remarkable qualitative changes in the picture of the color superconducting (CSC) phase formation. This concerns, in particular, the possibility of a transition to the CSC phase and diquark condensation at finite temperature.

hep-ph↗
arXiv2001

Chromomagnetic Catalysis of Color Superconductivity and Dimensional Reduction

We consider diquark condensation in external chromomagnetic fields at non--zero temperature. The general features of this process are investigated for various field configurations in relation to their symmetry properties and the form of the quark spectrum. According to the fields, there arises dimensional reduction by one or two units. In all cases there exists diquark condensation even at arbitrary weak quark attraction, confirming the idea about universality of this mechanism in a chromomagnetic field. Possible influence of a nonzero chemical potential on the results obtained is also discussed.

hep-th↗
arXiv2001

Heavy quark potential and mass spectra of heavy mesons

The relativistic quark model is presented. The quark-antiquark potential for the Schroedinger-like equation is constructed with the account of retardation effects and one-loop radiative corrections. It consists of the one-gluon exchange part and the confining part which is the mixture of the Lorentz scalar and Lorentz vector contributions. The latter contains both the Dirac and Pauli terms. In the v^2/c^2 approximation the mass spectra of heavy quarkonia (charmonium and bottomonium) are calculated in good agreement with experiment. In the case of heavy-light mesons (B and D) the light quark is treated completely relativistically and only the expansion in the inverse heavy quark mass is used. The mass spectra of the ground and excited states of D, D_s, B, B_s mesons are calculated. They exhibit some features of the so-called ``level inversion''. The obtained results are generally in accord with experimental data. Still there exist some discrepancies between measurements of different collaborations.

hep-ph↗
arXiv2001

Chromomagnetic Catalysis of Chiral Symmetry Breaking and Color Superconductivity

It is shown in the framework of an extended NJL model with two flavors that some types of external chromomagnetic field induce the dynamical chiral or color symmetry breaking even at weakest attraction between quarks. It is argued also that an external chromomagnetic field, simulating the chromomagnetic gluon condensate of the real QCD-vacuum, might significantly influence the color superconductivity formation.

hep-ph↗
arXiv2001

Non-abelian plane waves and stochastic regimes for (2+1)-dimensional gauge field models with Chern-Simons term

An exact time-dependent solution of field equations for the 3-d gauge field model with a Chern-Simons (CS) topological mass is found. Limiting cases of constant solution and solution with vanishing topological mass are considered. After Lorentz boost, the found solution describes a massive nonlinear non-abelian plane wave. For the more complicate case of gauge fields with CS mass interacting with a Higgs field, the stochastic character of motion is demonstrated.

hep-th↗
arXiv2001

Form factors of heavy-to-light B decays at large recoil

General relations between the form factors of B decays to light mesons are derived using the heavy quark and large recoil expansion. On their basis the complete account of contributions of second order in the ratio of the light meson mass to the large recoil energy is performed. Both ground and excited final meson states are considered. It is shown that most of the known form factor relations remain valid after the inclusion of quadratic mass corrections. The validity of some of such relations requires additional equalities for the helicity amplitudes. It is found that all these relations and equalities are fulfilled in the relativistic quark model based on the quasipotential approach in quantum field theory. The contribution of 1/m_b corrections to the branching fraction of the rare radiative B decay is discussed.

hep-ph↗
arXiv2001

Rare radiative B decays to orbitally excited K mesons

The exclusive rare radiative B meson decays to orbitally excited axial-vector mesons K_1^*(1270), K_1(1400) and to the tensor meson K_2^*(1430) are investigated in the framework of the relativistic quark model based on the quasipotential approach in quantum field theory. These decays are considered without employing the heavy quark expansion for the s quark. Instead the s quark is treated to be light and the expansion in inverse powers of the large recoil momentum of the final K^{**} meson is used to simplify calculations. It is found that the ratio of the branching fractions of rare radiative B decays to axial vector K^*_1(1270) and K_1(1400) mesons is significantly influenced by relativistic effects. The obtained results for B decays to the tensor meson K_2^*(1430) agree with recent experimental data from CLEO.

hep-ph↗
arXiv2001

Exclusive weak B decays to excited meson states

Exclusive semileptonic B decays to radially excited charmed mesons and rare radiative B decay to the orbitally excited tensor K_2^*(1430) meson are investigated in the framework of the relativistic quark model based on the quasipotential approach in quantum field theory. The heavy quark expansion is applied for the semileptonic B\to D^{(*)}'eνdecays. Both relativistic and the 1/m_Q corrections are found to play an important role for these decays and substantially modify results. For rare radiative B -> K_2^*(1430)γdecay such an expansion is not used for the s quark. Instead we apply the expansion in inverse powers of large recoil momentum of final K_2^*(1430) meson. The calculated branching fraction BR(B -> K_2^*(1430)γ)=(1.7\pm 0.6)\times 10^{-5} as well as the ratio BR(B -> K_2^*(1430)γ)/BR(B -> K^*(892)γ)=0.38\pm 0.08 are found to be in a good agreement with recent experimental data from CLEO.

hep-ph↗
arXiv2000

Chromomagnetic Catalysis of Color Superconductivity in a (2+1)-dimensional NJL Model

The influence of a constant uniform external chromomagnetic field $H$ on the formation of color superconductivity has been investigated. The consideration was performed in the framework of a (2+1)-dimensional Nambu--Jona-Lasinio model with two different four-fermionic structures responsible for $<\bar qq>$ and diquark $ $ condensates. In particular, it was shown that there exists a critical value $H_c$ of the external chromomagnetic field such that at $H>H_c$ a nonvanishing diquark condensate is dynamically created (the so-called chromomagnetic catalysis effect of color superconductivity). Moreover, external chromomagnetic fields may in some cases enhance the diquark condensate of color superconductivity.

hep-ph↗
arXiv2000

Rare radiative B decay to the orbitally excited K_2^*(1430) meson

The exclusive rare radiative B meson decay to the orbitally excited tensor K_2^*(1430) meson is investigated in the framework of the relativistic quark model based on the quasipotential approach in quantum field theory. The calculated branching ratio BR(B --> K_2^*(1430)γ)=(1.7\pm 0.6)\times 10^{-5} as well as the ratio BR(B --> K_2^*(1430)γ)/BR(B --> K^*(892)γ)=0.38\pm 0.08 is found in a good agreement with recent experimental data from CLEO.

hep-ph↗
arXiv2000

Scalar Mesons in a Chiral Quark Model with Glueball

Ground-state scalar isoscalar mesons and a scalar glueball are described in a U(3)xU(3) chiral quark model of the Nambu--Jona-Lasinio (NJL) type with 't Hooft interaction. The latter interaction produces singlet-octet mixing in the scalar and pseudoscalar sectors. The glueball is introduced into the effective meson Lagrangian as a dilaton on the base of scale invariance. The mixing of the glueball with scalar isoscalar quarkonia and amplitudes of their decays into two pseudoscalar mesons are shown to be proportional to current quark masses, vanishing in the chiral limit. Mass spectra of the scalar mesons and the glueball and their main modes of strong decay are described.

hep-ph↗
arXiv2000

Relativistic quark-antiquark potential and heavy quarkonium mass spectra

A general approach to accounting for retardation effects in the long-range (confining) part of the quark-antiquark potential is presented. The charmonium and bottomonium mass spectra are calculated with the systematic account of relativistic and retardation effects and the one-loop radiative corrections. A good fit to available experimental data on the mass spectra is obtained.

hep-ph↗
arXiv2000

Exclusive semileptonic B decays to excited D mesons

Exclusive semileptonic B decays to orbitally and radially excited charmed mesons are investigated in the first order of the heavy quark expansion. The emerging leading and subleading Isgur-Wise functions are calculated in the framework of the relativistic quark model. It is found that both relativistic and the 1/m_Q corrections play an important role and substantially modify results. An interesting interplay between different corrections is observed.

hep-ph↗
arXiv1999

Exclusive semileptonic B decays to radially excited D mesons

Exclusive semileptonic B decays to radially excited charmed mesons are investigated at the first order of the heavy quark expansion. The arising leading and subleading Isgur-Wise functions are calculated in the framework of the relativistic quark model. It is found that the 1/m_Q corrections play an important role and substantially modify results. An interesting interplay between different corrections is found. As a result the branching ratio for the B-> D'eνdecay is essentially increased by 1/m_Q corrections, while the one for B-> D*'eνis only slightly influenced by them.

hep-ph↗