Isospin breaking in scalar and pseudoscalar channels of radiative J/ψJ/\psi-decays

In the framework of simple assumption on factorizing a mixing of vector state with isoscalar components in effective amplitudes of isospin breaking caused by the electromagnetic quark current, a branching fraction of radiative $J/\psi\to a_0$ transition is evaluated at the level of $3\cdot 10^{-3}$.Comment: 3 pages, revtex4 class, 2 eps-figures; reference, comment and acknowledgement adde

Gold-plated Mode of CP-Violation in Decays of B_c Meson from QCD Sum Rules

The model-independent method based on the triangle ideology is implemented to extract the CKM-matrix angle gamma in the decays of doubly heavy long-lived meson B_c. We analyze a color structure of diagrams and conditions to reconstruct two reference-triangles by tagging the flavor and CP eigenstates of D^0 meson in the fixed exclusive channels. The characteristic branching ratios are evaluated in the framework of QCD sum rules.Comment: 11 pages, RevTeX4 file, 4 eps-figure

Gravitational lensing due to dark matter modelled by vector field

The specified constant 4-vector field reproducing the spherically symmetric stationary metric of cold dark matter halo in the region of flat rotation curves results in a constant angle of light deflection at small impact distances. The effective deflecting mass is factor $\pi/2$ greater than the dark matter mass. The perturbation of deflection picture due to the halo edge is evaluated.Comment: 17 pages, LaTeX iopart class, 10 eps figures; explanaitions and discussion are extended and improved, reference added; version to appear in Classical and Quantum Gravit

Origin of Pure Spin Superradiance

The question addressed in this paper is: What originates pure spin superradiance in a polarized spin system placed inside a resonator? The term "pure" means that no initial coherence is imposed on spins, and its appearance manifests a purely self-organized collective effect. The consideration is based on a microscopic model with dipole spin interactions. An accurate solution of evolution equations is given. The results show that the resonator Nyquist noise does not play, contrary to the common belief, any role in starting spin superradiance, but the emergence of the latter is initiated by local spin fluctuations. The decisive role of nonsecular dipole interactions is stressed.Comment: 1 file, 13 pages, RevTe

Centipede ladder at quarter filling

We study the ground state and excitation spectrum of a quasi one-dimensional nanostructure consisting of a pole and rungs oriented in the opposite directions ("centipede ladder", CL) at quarter filling. The spin and charge excitation spectra are found in the limits of small and large longitudinal hopping $t_\|$ compared to the on-rung hopping rate $t_\perp$ and exchange coupling $I_\perp$. At small $t_\|$ the system with ferromagnetic on-rung exchange demonstrates instability against dimerization. Coherent propagation of charge transfer excitons is possible in this limit. At large $t_\|$ CL behaves like two-orbital Hubbard chain, but the gap opens in the charge excitation spectrum thus reducing the symmetry from SU(4) to SU(2). The spin excitations are always gapless and their dispersion changes from quadratic magnon-like for ferromagnetic on-rung exchange to linear spinon-like for antiferromagnetic on-rung exchange in weak longitudinal hopping limit.Comment: 10 pages, 7 eps figure

Processes e+e−→ccˉccˉe^+e^- \to c \bar c c \bar c and e+e−→J/ψ+gge^+e^- \to J/\psi +gg at s=10.59\sqrt{s}=10.59 GeV

BELLE Collaboration data for $J/\psi$ inclusive production in the processes $e^+e^-\to J/\psi+gg$ and $e^+e^-\to J/\psi +c\bar c$ have been discussed. These data have been compared with the predictions of two pQCD methods: the former method use the information about the $J/\psi$ wave function, the latter one do not use such information and is based on the quark-hadron duality hypothesis. Both these calculation methods lead to essential discrepancy between the theoretic predictions and the experimental data. The production cross section dependence on effective gluon mass has been investigated for the process $e^+e^-\to J/\psi+gg$. The production cross section of doubly charmed baryons $\Xi ^{*}_{cc}$ has been estimated.Comment: 9 pages, 4 figures. In this version of the paper several important references have been adde

One-Loop Corrections to Bubble Nucleation Rate at Finite Temperature

We present an evaluation of the 1-loop prefactor in the lifetime of a metastable state which decays at finite temperature by bubble nucleation. Such a state is considered in one-component phi^4 model in three space dimensions. The calculation serves as a prototype application of a fast numerical method for evaluating the functional determinants that appear in semiclassical approximations.Comment: DO-TH-93/18, 15 pages, 11 Figures available on request, LaTeX, no macros neede

Branching ratios of Bc Meson Decaying to Pseudoscalar and Axial-Vector Mesons

We study Cabibbo-Kobayashi-Maskawa (CKM) favored weak decays of Bc mesons in the Isgur-Scora-Grinstein-Wise (ISGW) quark model. We present a detailed analysis of the Bc meson decaying to a pseudoscalar meson (P) and an axial-vector meson (A). We also give the form factors involving transition in the ISGW II framework and consequently, predict the branching ratios of decays.Comment: 19 pages,7 table

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