3,695 research outputs found
Small cosmological constant in seesaw mechanism with breaking down SUSY
The observed small value of cosmological constant can be naturally related
with the scale of breaking down supersymmetry in agreement with other
evaluations in particle physics.Comment: 12 pages, revtex4 class, 2 eps-figure
Prospects for the Bc Studies at LHCb
We discuss the motivations and perspectives for the studies of the mesons of
the (bc) family at LHCb. The description of production and decays at LHC
energies is given in details. The event yields, detection efficiencies, and
background conditions for several Bc decay modes at LHCb are estimated.Comment: 20 pages, 5 eps-figure
Estimation of damping model correctness using experimental modal analysis
This paper is dedicated to the damping identification problem. Short outlook of damping identification methods is given in the first part of the paper. All these methods can successfully identify internal damping of free-moving structures but it becomes problematically to correctly estimate damping forces when the structure is fixed and there are some joints. The recent methods of structural damping identification don’t give a full understanding of dissipation problem too. An explanation of damping-frequency relation features based on the existence of another damping nature, external damping for example, is proposed in this paper. These assumptions are demonstrated by the modal parameters identification of a turbine blade
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
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
Two-tone spectroscopy of a SQUID metamaterial in the nonlinear regime
Compact microwave resonantors made of superconducting rings containing
Josephson junctions (SQUIDs) are attractive candidates for building frequency
tunable metamaterials with low losses and pronounced nonlinear properties. We
explore the nonlinearity of a SQUID metamaterial by performing a two-tone
resonant spectroscopy. The small-amplitude response of the metamaterial under
strong driving by a microwave pump tone is investigated experimentally and
theoretically. The transmission coefficient of a weak probe signal is
measured in the presence of the pump tone. Increasing the power of the pump, we
observe pronounced oscillations of the SQUID's resonance frequency
. The shape of these oscillations varies significantly with
the frequency of the pump tone . The response to the probe
signal displays instabilities and sidebands. A state with strong second
harmonic generation is observed. We provide a theoretical analysis of these
observations, which is in good agreement with the experimental results
Theory of stripe domains in magnetic shape memory alloys
The evolution of multivariant patterns in thin plates of magnetic shape
memory materials with an applied magnetic field was studied theoretically. A
geometrical domain-model is considered composed of straight stripe-like
martensite variants with constant internal magnetization (high anisotropy
limit) and magnetic domain wall orientation fixed by the twin boundaries.
Through integral transforms of the demagnetization energy, the micromagnetic
energy is cast into a form convenient for direct numerical evaluation and
analytical calculations. The equilibrium geometrical parameters of multivariant
patterns with straight and oblique twin boundaries have been derived as
functions of the applied field and the material parameters of a plate. It is
shown that the oblique multivariant states exist only in plates with
thicknesses L larger than a certain critical value L_0. In samples with L < L_0
a magnetic-field-driven transformation occurs directly between single variant
states.Comment: Materials for E-MRS Fall Meeting, Warsaw 2007. Corrected 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
Spin and Charge Correlations in Quantum Dots: An Exact Solution
The inclusion of charging and spin-exchange interactions within the Universal
Hamiltonian description of quantum dots is challenging as it leads to a
non-Abelian action. Here we present an {\it exact} analytical solution of the
probem, in particular, in the vicinity of the Stoner instabilty point. We
calculate several observables, including the tunneling density of states (TDOS)
and the spin susceptibility. Near the instability point the TDOS exhibits a
non-monotonous behavior as function of the tunneling energy, even at
temperatures higher than the exchange energy. Our approach is generalizable to
a broad set of observables, including the a.c. susceptibility and the
absorption spectrum for anisotropic spin interaction. Our results could be
tested in nearly ferromagnetic materials.Comment: JETPL class, 6 pages, 2 figure
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