In the framework of potential models for heavy quarkonium the mass spectrum for the system (bc) is considered. Spin-dependent splittings, taking into account a change of a constant for effective Coulomb interaction between the quarks, and widths of radiative transitions between the (bc) levels are calculated. In the framework of QCD sum rules, masses of the lightest vector B * c and pseudoscalar B c states are estimated, scaling relation for leptonic constants of heavy quarkonia is derived, and the leptonic constant f B C is evaluated.

Spectra of masses are calculated for the families of doubly heavy baryons in the framework of the nonrelativistic quark model with the QCD potential of Buchmüller and Tye. We suppose the quark-diquark structure for the wave functions and take into account the spin-dependent splittings. The physical reasons causing the existence of quasistable excited states in the subsystem of heavy diquark are considered for the heavy quarks of identical flavors.

Gershtein S.S., Kiselev V.V., Likhoded A.K., Tkabladze A.V. Physics of B c mesons: IHEP Preprint 94-81. -Protvino, 1994. -p. 82, figs. 23, tables 28. In the framework of potential models for heavy quarkonium the mass spectrum for the system (bc) is considered. Spin-dependent splittings, taking into account a change of a constant for effective coulomb interaction between the quarks, and widths of radiative transitions between the (bc) levels are calculated. In the framework of QCD sum rules, masses of the lightest vector B * c and pseudoscalar B c states are estimated, scaling relation for leptonic constants of heavy quarkonia is derived, and the leptonic constant f Bc is evaluated. The B c decays are considered in the framework of both the potential models and the QCD sum rules, where the significance of Coulomb-like corrections is shown. The relations, following from the approximate spin symmetry for the heavy quarks in the heavy quarkonium, are analysed for the form factors of the semileptonic weak exclusive decays of B c . The B c lifetime is evaluated with the account of the corrections to the spectator mechanism of the decay, because of the quark binding into the meson. The total and differential cross sections of the B c production in different interactions are calculated. The analytic expressions for the fragmentational production cross sections of B c are derived. The possibility of the practical B c search in the current and planning experiments at electron-positron and hadron colliders is analysed.

In this paper we show that heavy quarckonium states, similar to light mesons, form Regge trajectories in (n, M 2 ) and (M 2 , J) planes and the slope of these trajectories is independent on the quantum numbers of the mesons. This fact can be useful for the prediction of the masses of heavy quarkonia and the determination of the quantum numbers of the newly discovered states.

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