Physics of $B_c$-mesons

The mass spectrum for the system $(\overline bc)$ is considered in the framework of potential models for the heavy quarkonium. Spin-dependent splittings, with account taken of the change of a constant representing the effective Coulomb interaction between the quarks, and widths of radiative transitions between the $(\overline bc)$ levels are calculated. In the framework of QCD sum rules, the masses of the lightest vector $B_c^*$ and pseudoscalar $B_c$ states are estimated, the scaling relation for leptonic constants of heavy quarkonia is derived, and the leptonic constant $f_{B_c}$ is evaluated. The $B_c$ decays are considered in the framework both of the potential models and of the QCD sum rules. 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 account taken 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 search for $B_c$ in current and planned experiments at electron–positron and hadron colliders is analysed.