Search

We present analytical results on the two-loop anomalous dimensions of currents for baryons, containing two heavy quarks $J = [Q^{iT}C\Gamma\tau Q^j]\Gamma' q^k\epsilon_{ijk}$ with arbitrary Dirac matrices $\Gamma$ and $\Gamma'$ in the framework of NRQCD in the leading order over both the relative velocity of heavy quarks and the inverse heavy quark mass. It is shown, that in this approximation the anomalous dimensions do not depend on the Dirac structure of the current under consideration., Comment: Latex file, 13 page, 1 postscript figure

Using the quark-diquark approximation in the framework of Buchm\" uller-Tye potential model, we investigate the spectroscopy of doubly charmed baryons: $\Xi_{cc}^{++}$ and $\Xi_{cc}^{+}$. Our results include the masses, parameters of radial wave functions of states with the different excitations of both diquark and light quark-diquark system. We calculate the values of fine and hyperfine splittings of these levels and discuss some new features, connected to the identity of heavy quarks, in the dynamics of hadronic and radiative transitions between the states of these baryons., Comment: 10 pages, Latex file, 1 fig, corrected some typos

We have performed a detailed investigation of total lifetimes for the $\Xi_{cc}^{++}$ and $\Xi_{cc}^{+}$ baryons in the framework of operator product expansion over the inverse mass of charmed quark, whereas, to estimate matrix elements of operators obtained in OPE, some approximations of nonrelativistic QCD are used. This approach allows one to take into account the corrections to the spectator decays of $c$-quarks, which reflect the fact, that these quarks are bound, as well as the contributions, connected to the effects of both the Pauli interference for the $\Xi_{cc}^{++}$-baryon and the weak scattering for the $\Xi_{cc}^{+}$-baryon. The realization of such program leads to the following estimates for the total lifetimes of doubly charmed baryons: $\tau_{\Xi_{cc}^{++}}=0.43\pm 0.1~ps$ and $\tau_{\Xi_{cc}^{+}}=0.11\pm 0.01~ps$., Comment: 15 pages, Latex file, 3eps figes

A model is constructed for a chiral abelian gauge-interaction of fermions and a potential of three higgses, so that the potential possesses a discrete symmetry of the vacuum state, which provides the introduction of three generations for the fermions. For the model including charged currents, a matrix of the flavor mixing is described, and a phase giving the violation of CP-invariance is determined. Some approximate relations connecting the values of mixing matrix to the mass ratios for the fermions in different generations are derived., Comment: 19 pages, Latex file, 2 eps-figures, minor corrections added

Theoretical predictions on the $B_c$ meson properties are reviewed., Comment: 28 pages, Latex file with 12 ps-figures

The fragmentation function of a scalar leptoquark into possible S-wave bound states with a heavy anti-quark is calculated to the leading order in perturbative QCD for the high energy processes at large transverse momenta. The one-loop equations for the $q^2$-evolution of moments of the fragmentation function due to the hard gluon emission by the leptoquark are derived. The integral probabilities of fragmentation are evaluated., Comment: 8 pages, epsf-style, 3 eps-figures

Calculations of cross-sections for the gluon-photon production of $B_c$ and $B_c^*$ mesons as well as for the production in $ep$-interactions at HERA are performed in the leading order of perturbative QCD. We show that the nonabelian structure of QCD leads to an essential forward-backward asymmetry in these processes., Comment: 14 pages, epsf-style, 8 ps-figures

In the leading order of perturbative QCD one calculates the total and differential cross-sections for the hadronic production of doubly charmed baryons $\Xi_{cc}$ and $\Xi_{cc}^*$ in different experiments. The experimental evaluation of cross-sections for the $J/\Psi +D + \bar D$ production would allow one to decrease the uncertainty in the determination of cross-sections for the doubly charmed baryons due to the choice of $\alpha_s$ and $m_c$. One shows that in the HERA-B and E781 experiments with fixed tagets the suppression of the $\Xi_{cc}$ and $\Xi_{cc}^*$ production to the yield of $c \bar c$-pairs is the value of the order of $10^{-6}-10^{-5}$, whereas at the TEVATRON and LHC colliders it is about $10^{-4}-10^{-3}$. In the E781 experiment the observation of $\Xi_{cc}$ and $\Xi_{cc}^*$ is practically unpossible. At the HERA-B and TEVATRON facilities one can expect $10^5$ events with the double charm, and at LHC one has about $10^9$ ones., Comment: 30 pages, epsf-style, 12 figures

In the model with the spontaneous breaking of chiral gauge symmetry, the vacuum structure for the pair of Higgs fields can provide the introduction of two generations of fermions. The mixing matrix of charged currents is determined., Comment: 8 pages, some explanations and references are added

In the framework of perturbative QCD and potential models of heavy quarkonium, total cross-sections and differential characteristics of hadronic production for different spin states of the $B_c$-meson family are calculated at energies of LHC. Theoretical predictions for masses and branching ratios of $B_c$ decays are given, which allows one to make estimates for an expected number of reconstructed events with $B_c$., Comment: 27 pages, Latex file, epsf-style, 6 ps-figures

The value of $\alpha_s(m_Z)=0.106\pm 0.005$ is obtained in a scheme of sum rules for the leptonic constants of the vector $nS$-levels in the heavy $(\bar b b)$-quarkonium., Comment: 5 pages, latex

The decay constant for the vector state of $3S$-level in the heavy $(\bar b c)$-quarkonium is evaluated in the framework of sum rules for the mesonic currents. A scaling relation for the constants of vector quarkonia with different quark contents is derived. The numerical estime gives $\Gamma(B_c^{*+}(3S)\to B^+D^0)=90 \pm 35$ MeV., Comment: 6 pages, Revtex

The two-particle decays of B_c^+ to psi pi^+(rho^+) and B_c^+ to eta_c pi^+(rho^+) are considered in a way taking into account a soft binding of quarks in the heavy quarkonia and a hard gluon exchange between the constituents at large recoil momenta of psi(eta_c). An approximate double enhancement of the amplitudes is found because of the nonspectator t-channel contribution., Comment: 7 pages, 1 eps-figure, eqs.(4), (6) corrected, numerical estimates changed

In the framework of perturbative QCD in the fourth order over the $\alpha_s$ coupling constant for the production of two pairs of quarks and in the model of weak binding of the quarks into meson, the analysis of the hadronic production of mesons, containing $b$-quark, is performed, and a minimal transverse momentum is determined, so that at the momenta greater than the found one, the meson differential spectrum can be reliably described in the model of factorization of the hard $b$-quark production and the subsequent fragmentation into the mesons. At low transverse momenta of the meson, nonfragmentational contributions are essential. They are determined by the complete set of QCD diagrams in the given order over $\alpha_s$, so that the latters result in the effect of destructive interference with the diagrams of fragmentation at $z=2E/\sqrt{s}$ close to $1$., Comment: 9 pages, LATEX file, 6 figures

Using a quite accurate flavour-independence of $nS$-level mass differences in heavy quarkonia and a corresponding quasiclassical expression for the heavy quark binding energy, one shows that experimental data on masses of mesons with heavy quarks allow one to make the estimate $\bar \Lambda= 0.63\pm 0.03$ GeV., Comment: 7 pages, LATEX file

In the framework of sum rules with a use of quarkonium mass spectrum, evaluated in the quasiclassical approximation, estimates of leptonic constant $f_B^{stat}\simeq 320\pm 60$ MeV in a static limit and for the average heavy quark momentum squared $\mu_\pi^2 \simeq 0.5\pm 0.1$ GeV$^2$ are obtained., Comment: 7 pages, LATEX file

In the leading $O(\alpha_s^4)$ order of the perturbative QCD, the hadronic production cross-sections of $S$- and $P$-wave states of $B_c$ meson are calculated. The results for the $S$-wave levels are compared with the values given in other papers as well as in the model of the $b$ quark fragmenatation into $B_c$. In the given order, the cross-sections of the hadronic production of the $P$-wave states are calculated for the first time. Their contribution into the $B_c$ meson production is less than 10\%. There is a strong difference between the predictions of the fragmentation model and the exact perturbative calculations. These difeerences are discussed in details for the differential distributions over various kinematical quantities., Comment: 12 pages, LATEX file, ps-figures. uuencoded compresed tar-file

Numerical calculations for the production of $P$-wave levels of $B_c$ quarkonium in $\gamma\gamma$ collisions are performed in the leading $O(\alpha_s^2\alpha_{em}^2)$ order of perturbation theory. The total cross-section of $P$-wave state production is about 10 \% of that for the $S$-wave levels. The contribution of fragmentation component ($6+6$ diagrams) is low, and the basic contribution is determined by the recombination mechanism ($8$ Feynman diagrams). The gauge invariant term of the $\bar b\to B_c$ fragmentation ($6$ diagrams) quite accurately reproduces the result of the fragmentation model, whereas there is a strong deviation of the $c\to B_c$ fragmentation term from the predictions of the fragmentation model., Comment: 7 pages, REVTEX file, 6 figures (uuencoded compressed tar-file)

In the framework of QCD perturbation theory, total and differential cross sections of the $\Xi_{bc}'$, $\Xi_{bc}^{(*)}$ and $\Xi_{cc}^{(*)}$ baryons production in gluon collisions are calculated in the leading order over $\alpha_s$ for the doubly heavy ($b c$) and ($ c c$) diquarks. At both small and large transverse momenta of the baryons, a use of the mechanism of the heavy quark fragmentation into the heavy diquark is shown to underestimate the cross section values in comparison with the exact numerical calculations of complete set of diagrams. The expected in Tevatron experiments yield of baryons with two heavy quarks is evaluated as $(1.3\pm 0.3) \cdot 10^5 \,\, bcq$-baryons and $(1.6\pm 0.3) \cdot 10^4 \,\, ccq$-baryons at $p_T>5$ GeV and $|y|<1$ of the baryon momentum and rapidity cuts, with account for the antiparticle yields., Comment: 7 pages, LATEX file and tar-compressed uuencoded figures

In the framework of renormalon consideration, a role of the anomalous dependence of gluon propagator on the scale $\mu$ is shown for a large number of quark flavours as well as in the nonabelian theory, where the parameter of the "running" coupling constant evolution has a hidden dependence on the scale. A phenomenological matching between the modified renormalon and the static quark potential is described to fix the renormalon scales., Comment: 13 pages, LATEX file

In the framework of renormalon consideration in the approximation of a large number of quark flavours, a role of the anomalous dependence of gluon propagator on the scale $\mu$ is shown., Comment: 6 pages, LATEX file

The width of $B_c^+\to \psi \pi^+$ decay is calculated in the framework of factorization of a hard gluon exchange and a soft binding of quarks in the heavy quarkonium, so that ${\rm BR}(B_c^+\to \psi \pi^+) = 2.0\pm 0.5$ \%., Comment: 8 pages, LATEX file

In the framework of potential models for heavy quarkonium the mass spectrum for the system ($\bar b c$) 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 ($\bar b c$) 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. 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 future experiments at electron-positron and hadron colliders is analysed., Comment: 81 page, latex, ihep.sty is required and attached in the end of the file after \end{document}, figures are not available

The modification of the naive potential model of the heavy meson is considered on the basis of the single-time prescription for the quark-meson form factor and the covariant choice of the quatk relative momentum. The application of the model to the description of the semileptonic decays of the beauty meson allows one to determine the Isgur-Wise function slope $\rho^2\simeq 1.25$ and to extract the value $|V_{bc}|= 0.038\pm 0.003$ from the experimental data., Comment: Preprint IHEP 94-97, 12 LATEX pages

In a specific scheme of the QCD sum rules, one gives the estimate of $\alpha_S\simeq 0.20$ from the data on the masses and leptonic constants of $\psi$- and $\Upsilon$-particles., Comment: Preprint IHEP 94-92, 2 LATEX pages

Using a specific scheme of the QCD sum rules for heavy quarkonium in the leading approximation over the inverse heavy quark mass, one gets the estimate of the difference between the masses of the heavy meson and heavy quark $\bar \Lambda = 0.59\pm 0.02$ GeV., Comment: Preprint IHEP 94-89, 4 LATEX pages

The cross-section for the double charmed baryon production at a $B$-factory is estimated on the basis of the perturbative QCD calculations for the $c c$-diquark production as well as of the quark-hadron duality., Comment: Prepint IHEP 94-56, 7 LATEX pages, figures are not avaleble

Using a specific scheme of the QCD sum rules, one derives the relation for leptonic constants of $nS$-wave heavy qiarkonia, so $f^2_{n_1}/f^2_{n_2}= n_2/n_1$, that does not depend on the quarkonium content, and it is in a good agreement with the experimental values of constants for the $\psi$- and $\Upsilon$-families., Comment: Preprint IHEP 94-71, LATEX, 17 pages

In the framework of a specific scheme of the QCD sum rules for $S$-wave levels of the heavy quarkonium, one derives an expression, relating the energetic density of quarkonium states and universal characteristics in the heavy quarkonium physics, such as the difference between the masses of a heavy quark $Q$ and meson $(Q\bar q)$ and the number of heavy quarkonium levels below the threshold of $(Q\bar Q) \to (Q\bar q) + (\bar Q q)$ decay., Comment: Preprint IHEP 94-75, LATEX, 22 pages

Using a specific scheme of the QCD sum rules, one derives an universal formula for the mass differences for the $nS$-levels of heavy qiarkonium. This relation does not depend on the flavours of the heavy quarks, composing the quarkonium, and it is in a good agreement with the experimental mass values for the $\psi$- and $\Upsilon$-families., Comment: Preprint IHEP 94-74, LATEX, 12 pages

In the framework of potential models for heavy quarkonium the mass spectrum for the system ($\bar b c$) 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 ($\bar b c$) 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., Comment: IHEP 94-51, LATEX, 39 pages

In the framework of QCD sum rules one uses a scheme, allowing one to apply the conditions of both nonrelativistic heavy quark motion inside mesons and independence of nonsplitting nS-state density on the heavy quark flavours. In the leading order an analitic expression is derived for leptonic constants of both heavy quarkonia and heavy mesons with a single heavy quark. The expression allows one explicitly to determine scaling properties of the constants., Comment: IHEP 94-63, Protvino, Standard LATEX, 17 pages

We assume that a rather large bag of the $\Upsilon''(3S b\bar b)$ heavy quarkonium is in the phase of spontaneously broken chiral symmetry, in contrast to the $\Upsilon(1S b \bar b)$ hadron bag, having small size and being in the phase of exact chiral symmetry, so that the shift of the phases in the $\Upsilon'' \to \Upsilon \pi \pi$ transition is the additional source for the $\pi\pi$ pairs. This source causes an anomalous $\pi\pi$ invariant mass distribution, which is experimentally observed., Comment: 20 pages, IHEP 94-46, Protvino, Russia

The cross-section for the production of $b{\bar b} c{\bar c}$ quarks in $e^+e^-$ annihilation, that proves to be at a level of $\sigma (e^+e^- \rightarrow b{\bar b} c{\bar c})/ \sigma (e^+e^- \rightarrow b{\bar b}) \sim 10^{-2}$ for ${\sqrt s}=M_Z$ is calculated within the frames of the QCD perturbation theory. The cross sections for the associated production of $1S$- and $2S$-wave states of $B_c$-meson in the reaction $e^+e^- \rightarrow B_c b{\bar c}$ were calculated in the nonrelativistic model of a heavy quarkonium. The fragmentation function of $b\to B_c^{(*)}$ is analysed in the scaling limit. The number of $\Lambda_{bc}$-hyperons to be expected at LEP is estimated on the basis of the assumption on quark-hadron duality., Comment: Standard LATEX 16 pages, 10 Figs. (unavalibale)

Sum rules for exclusive production of heavy meson pairs in $e^+e^-$ annihilation are used to evaluate the $\Upsilon(4S) \to B \bar B$ and $\psi(3770) \to D \bar D$ decay widths. Infinitely heavy quark limit is discussed, so that scaling law for the quarkonium-meson coupling constant is derived. A value of the $B\bar B$ pair contribution into the leptonic constant $f_{\Upsilon(4S)}$ is estimated., Comment: 14 pages, 1 Fig., Standard LATEX