Baryons with two heavy quarks

We consider general physical characteristics of doubly heavy baryons: the spectroscopy in the framework of potential approach and sum rules of QCD, mechanisms of production in various interactions on the basis of fragmentation model with account of preasymptotic corrections caused by higher twists over the transverse momentum of baryon, inclusive decays and lifetimes in the operator product expansion over the inverse powers of heavy quark masses as well as the exclusive decays in the sum rules of QCD. We generalize the methods developed in the effective theory of heavy quarks towards the description of systems with two heavy quarks and a single light quark. The calculations are presented for the masses, decay widths and yields of baryons with two heavy quarks in the running and planned experimental facilities. We discuss the prospects of search for the baryons and possibilities of experimental observation. The most bright physical effects concerning these baryons as well as their position in the system for the theoretical description of heavy quark dynamics are considered.Comment: review, LaTeX file, 32 postscript figure

Lifetimes of Xi_{bc}^{+} and Xi_{bc}^{0} baryons

Estimates of lifetimes and partial branching ratios for the baryons $\Xi_{bc}^{+}$ and $\Xi_{bc}^{0}$ are presented using the inverse heavy quark mass expansion technique carried out in the Operator Product Expansion approach. We take into account both the perturbative QCD corrections to the spectator contributions and, depending on the quark contents of hadrons, the Pauli interference and weak scattering effects between the constituents, using a potential model for the evaluation of the non-perturbative parameters.Comment: 15 pages, LATEX file, 2 eps-figure

Light hadron production in Bc→Bs(∗)+XB_{c}\to B_{s}^{(*)}+X decays

The article is devoted to Bc->Bs+n pi, Bc->Bs*+n pi decays with n=1, 2, 3, 4. In the framework of factorization theorem the branching fractions of these processes can be written as convolution of hard part, describing Bc->Bs W, Bc->Bs* W vertices, and spectral functions, that correspond to transition of virtual $W$-boson into a final pi-meson system. These functions were obtained from the fit of experimental data on $\tau$-lepton decay and electron-positron annihilation. Using different sets of Bc->Bs decay form-factors we present branching fractions and distributions over the invariant mass of the final pi-meson system.Comment: minor changes, some references adde