2,672 research outputs found
Short-Wave Excitations in Non-Local Gross-Pitaevskii Model
It is shown, that a non-local form of the Gross-Pitaevskii equation allows to
describe not only the long-wave excitations, but also the short-wave ones in
the systems with Bose-condensate. At given parameter values, the excitation
spectrum mimics the Landau spectrum of quasi-particle excitations in superfluid
Helium with roton minimum. The excitation wavelength, at which the roton
minimum exists, is close to the inter-particle interaction range. It is shown,
that the existence domain of the spectrum with a roton minimum is reduced, if
one accounts for an inter-particle attraction.Comment: 5 pages, 5 figures, UJP style; presented at Bogolyubov Kyiv
Conference "Modern Problems of Theoretical and Mathematical Physics",
September 15-18, 200
Two-color interference stabilization of atoms
The effect of interference stabilization is shown to exist in a system of two
atomic levels coupled by a strong two-color laser field, the two frequencies of
which are close to a two-photon Raman-type resonance between the chosen levels,
with open channels of one-photon ionization from both of them. We suggest an
experiment, in which a rather significant (up to 90%) suppression of ionization
can take place and which demonstrates explicitly the interference origin of
stabilization. Specific calculations are made for H and He atoms and optimal
parameters of a two-color field are found. The physics of the effect and its
relation with such well-known phenomena as LICS and population trapping in a
three-level system are discussed.Comment: the paper includes 1 TeX file and 16 picture
The gamma-ray telescope Gamma-1
French and Soviet specialists have designed and built the gamma-ray telescope GAMMA-1 to detect cosmic gamma rays above 50 MeV. The sensitive area of the detector is 1400 sq cm, energy resolution is 30% at 300 MeV, and angular resolution 1.2 deg at 300 MeV (and less than 20' arc when a coded aperture mask is used). Results on calibration of the qualification model and Monte-Carlo calculations are presented
Critical and non-critical coherence lengths in a two-band superconductor
We study the peculiarities of coherency in a two-gap superconductor. The both
intraband couplings, inducing superconductivity in the independent bands, and
interband pair-transfer interaction have been taken into account. On the basis
of the Ginzburg-Landau equations derived from the Bogoliubov-de Gennes
equations and the relevant self-consistency conditions for a two-gap system, we
find critical and non-critical coherence lengths in the spatial behaviour of
the fluctuations of order parameters. The character of the temperature
dependencies of these length scales is determined by the relative contributions
from intra- and interband interaction channels.Comment: Accepted for publication in Journal of Superconductivity and Novel
Magnetis
Measurement of decay rate and parameters at KEDR
Using the inclusive photon spectrum based on a data sample collected at the
peak with the KEDR detector at the VEPP-4M collider, we
measured the rate of the radiative decay as well
as mass and width. Taking into account an asymmetric photon
lineshape we obtained keV, MeV/, MeV.Comment: 6 pages, 3 figure
Evidence of time-dependent CP violation in the decay B0 to D*+D*-
We report a measurement of the CP-odd fraction and the time-dependent CP
violation in B0 to D*+D*- decays, using 657.10^6 BBbar events collected at the
Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy
e+e- collider. We measure a CP-odd fraction of
Rperp=0.125+/-0.043(stat)+/-0.023(syst). From the distributions of the
proper-time intervals between a B0to D*+D*- decay and the other B meson in the
event, we obtain evidence of CP violation with measured parameters
AD*+D*-=0.15+/-0.13(stat)+/-0.04(syst) and
SD*+D*-=-0.96+/-0.25(stat)-0.16+0.13(syst).Comment: Published in PR
Measurement of J/psi to eta_c gamma at KEDR
We present a study of the inclusive photon spectra from 5.9 million J/psi
decays collected with the KEDR detector at the VEPP-4M e+e- collider. We
measure the branching fraction of radiative decay J/psi to eta_c gamma, eta_c
width and mass. Our preliminary results are: M(eta_c) = 2979.4+-1.5+-1.9 MeV,
G(eta_c) = 27.8+-5.1+-3.3 MeV, B(J/psi to eta_c gamma) = (2.34+-0.15+-0.40)%.Comment: To be published in Proceedings of the PhiPsi09, Oct. 13-16, 2009,
Beijing, Chin
- …