The B_c Meson Lifetime in the Light--Front Constituent Quark Model

We present an investigation of the total decay rate of the (ground state) B_c meson within the framework of the relativistic constituent quark model formulated on the light-front (LF). The exclusive semileptonic (SL) and nonleptonic (NL) beauty and charm decays of the B_c meson are described through vector and axial hadronic form factors, which are calculated in terms of a constituent quark model LF wave functions. The latter ones are derived via the Hamiltonian LF formalism using as input the update versions of the constituent quark model. The inclusive SL and NL partial rates are calculated within a convolution approach inspired by the partonic model and involving the same B_c wave function which is used for evaluation of the exclusive modes. The framework incorporates systematically 84 exclusive and 44 inclusive partial rates corresponding to the underlying \bar{b}\to\bar{c} and c\to s quark decays. Based on our approach we find\tau_{B_c}=0.59 \pm 0.06 ps where the theoretical uncertainty is dominated by the uncertainty in the choice of LF wave functions and the threshold values for the hadron continuum. For the branching fractions of the B^+_c \to J/\psi\mu^+\nu_{\mu} and B_c^+\to J/\psi\pi^+ decays we obtain 1.6 % and 0.1 %, respectively.Comment: 10 pages, LaTeX, 1 ps figur

Weak decays of the B_c meson to charmonium and D mesons in the relativistic quark model

Semileptonic and nonleptonic decays of the B_c meson to charmonium and D mesons are studied in the framework of the relativistic quark model. The decay form factors are explicitly expressed through the overlap integrals of the meson wave functions in the whole accessible kinematical range. The relativistic meson wave functions are used for the calculation of the decay rates. The obtained results are compared with the predictions of other approaches.Comment: 27 pages, 17 figures, 1 figure and 1 reference added, version to appear in Phys. Rev.

The semileptonic decays of the B_c meson

We study the semileptonic transitions B_c to \eta_c, J/\psi, D, D^*, B, B^*, B_s, B_s^* in the framework of a relativistic constituent quark model. We use experimental data on leptonic J/\psi decay, lattice and QCD sum rule results on leptonic B_c decay, and on radiative \eta_c transitions to adjust the quark model parameters. We compute all form factors of the above semileptonic B_c-transitions and give predictions for various semileptonic B_c decay modes including their \tau-modes when they are kinematically accessible. The implications of heavy quark symmetry for the semileptonic decays are discussed and are shown to be manifest in our explicit relativistic quark model calculation. A comparison of our results with the results of other calculations is performed.Comment: 31 pages Latex (uses epsf, revtex). Section II expanded, typos corrected. This version will appear in Phys. Rev.

Mass spectra of doubly heavy Omega_QQ' baryons

We evaluate the masses of baryons composed of two heavy quarks and a strange quark with account for spin-dependent splittings in the framework of potential model with the KKO potential motivated by QCD with a three-loop beta-function for the effective charge consistent with both the perturbative limit at short distances and linear confinement term at long distances between the quarks. The factorization of dynamics is supposed and explored in the nonrelativistic Schroedinger equation for the motion in the system of two heavy quarks constituting the doubly heavy diquark and the strange quark interaction with the diquark. The limits of approach, its justification and uncertainties are discussed. Excited quasistable states are classified by the quantum numbers of heavy diquark composed by the heavy quarks of the same flavor.Comment: 14 pages, revtex4-file, 3 eps-figures, 5 tables, typos correcte

Prognosis of complicated clinical course of varicose veins of lower extremities on the basis of analysis of phenotypic characteristics of connective tissue dysplasia

Aim: to identify the phenotypic characteristics of indeterminate connective tissue dysplasia, which help to predict the progression of varicose veins of lower extremities and disease recurrence after surgery. Material and Methods. The long-term results of surgical treatment of 60 patients with varicose veins of lower extremities in a 5-year period after phlebectomy were analyzed. The phenotypic characteristics of indeterminate connective tissue dysplasia were researched. 24 patients had recurrence of varicose veins of lower extremities associated with disease progression; 36 patients did not have recurrence of varicose veins of lower extremities. Results. All the patients demonstrated the signs of indeterminate connective tissue dysplasia, whereas their frequency was different. There were specified nine phenotypic characteristics of indeterminate connective tissue dysplasia, which were significantly more frequent for patients with recurrence of varicose vein disease of lower extremities: 1) postural abnormality, 2) flat foot, 3) skin pallor, 4) hyperextension of skin, 5) positive "wrist test", 6) positive "pollex test", 7) diastasis recti abdominis, 8) myopia, 9) hematomas which form quickly. Conclusion. The determined sum of phenotypic characters of indeterminate connective tissue dysplasia allows to predict progression of varicose vein disease of lower extremities, and offers new opportunities for improving the results of surgical treatment via developing special therapeutic measures aimed at improving lifestyle and dysplasia treatment

Surgical approach to patients with varicothrombophlebitis with undifferentiated dysplasia of connective tissue

Aim: to study the peculiar features of clinical course of acute varicothrombophlebitis and surgical approach to patients with undifferentiated dysplasia of connective tissue. Material and Methods. The features of undifferentiated dysplasia of connective tissue, character of clinical course of acute varicothrombophlebitis, remote results for 94 patients, who had had Troyanov — Trendelenburg's operation, were studied. Results. 70 patients (74,5%) with acute varicothrombophlebitis demonstrated more than four phenotypic characters which showed the presence of undifferentiated dysplasia of connective tissue. 22 patients (31,4%) with acute varicothrombophlebitis with undifferentiated dysplasia of connective tissue were proved to have the discrepancy between localization of acute varicothrombophlebitis clinical evidences and level of proximal part of thrombus in the lumen of great saphenous vein. During the remote observation period, 66 patients (94,3%) with acute varicothrombophlebitis with undifferentiated dysplasia of connective tissue had pheblectomy, as there was vertical and horizontal pathological venous reflux. Out of 24 patients (25,5%) with acute varicothrombophlebitis without undifferentiated dysplasia of connective tissue, only four patients (16,7%) needed thesecond stage of surgical treatment, because 20 patients (83,3%), in 6 months after Troyanov — Trendelenburg's operation, demonstrated the restoration of functional consistency of valves of great saphenous and perforating veins. Conclusion. When determining the indications for urgent disconnection of saphenofemoral junction for patients with acute varicothrombophlebitis and also when choosing surgical treatment approach during remote observation period, it is reasonable to examine the phenotypic characters of undifferentiated dysplasia of connective tissue.</p