20 research outputs found
On the double radiative decay of B_s-meson
B_s-meson double radiative decay is investigated in
frame of supersymmetric extension of the standard model. The branching ratio is
calculated. It is shown that for light Higgs particle and heigh
supersymmetric contribution into branching ratio is significunt large than
standard model estimate.Comment: 5 pages, latex, no figure
Semileptonic transition in three--point QCD sum rules and HQET with gluon condensate corrections
Taking into account the gluon condensate contributions, the form factors of
the semileptonic transition with are
calculated in the framework of the three point QCD sum rules. The heavy quark
effective theory limit of the form factors are also computed. The relevant
total decay width as well as the branching ratio are evaluated and compared
with the predictions of the other non-perturbative approaches.Comment: 27 Pages, 4 Figures and 4 Table
Propulsion efficiency of a dynamic self-assembled helical ribbon
We study the dynamic self-assembly and propulsion of a ribbon formed from paramagnetic colloids in a dynamic magnetic field. The sedimented ribbon assembles due to time averaged dipolar interactions between the beads. The time dependence of the dipolar interactions together with hydrodynamic interactions cause a twisted ribbon conformation. Domain walls of high twist connect domains of nearly constant orientation and negligible twist and travel through the ribbon. The particular form of the domain walls can be controlled via the frequency and the eccentricity of the modulation. The flux of twist walls—a true ribbon property absent in slender bodies—provides the thrust onto the surrounding liquid that propels this biomimetic flagellum into the opposite direction. The propulsion efficiency increases with frequency and ceases abruptly at a critical frequency where the conformation changes discontinuously to a flat standing ribbon conformation
Two-particle decays of B_c meson into charmonium states
The factorization of hard and soft contributions into the hadronic decays of
B_c meson at large recoils is explored in order to evaluate the decay rates
into the S, P and D-wave charmonia associated with rho and pi. The constraints
of approach applicability and uncertainties of numerical estimates are
discussed. The mode with the J/psi in the final state is evaluated taking into
account the cascade radiative electromagnetic decays of excited P-wave states,
that enlarges the branching ratio by 20-25%.Comment: 13 pages, LaTeX axodraw-style, 1 figure, 2 table
Inclusive pion double charge exchange on O-16 above the delta resonance
The forward inclusive pion double charge exchange reaction,
^{16}O(pi^-,pi^+)X, at T_0 = 0.50 and 0.75 GeV has been studied in the
kinematical region where an additional pion production is forbidden by
energy-momentum conservation. The experiment was performed with the SKS
spectrometer at KEK PS. The measured ratio of double charge exchange
cross-section for these energies dsigma(0.50 GeV)/dOmega / dsigma(0.75
GeV)/dOmega = 1.7 +/- 0.2, disagrees with the value of 7.2 predicted within the
conventional sequential single charge exchange mechanism. Possible reasons for
the disagreement are discussed in connection with the Glauber inelastic
rescatterings.Comment: 4 pages, 5 figure
Physics of B_c mesons
In the framework of potential models for heavy quarkonium the mass spectrum
for the system () 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 () levels
are calculated. In the framework of QCD sum rules, masses of the lightest
vector and pseudoscalar states are estimated, scaling relation
for leptonic constants of heavy quarkonia is derived, and the leptonic constant
is evaluated. The 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
. The 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 production in
different interactions are calculated. The analytic expressions for the
fragmentational production cross sections of are derived. The possibility
of the practical 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 availabl