14,973 research outputs found
A ring trap for ultracold atoms
We propose a new kind of toroidal trap, designed for ultracold atoms. It
relies on a combination of a magnetic trap for rf-dressed atoms, which creates
a bubble-like trap, and a standing wave of light. This new trap is well suited
for investigating questions of low dimensionality in a ring potential. We study
the trap characteristics for a set of experimentally accessible parameters. A
loading procedure from a conventional magnetic trap is also proposed. The
flexible nature of this new ring trap, including an adjustable radius and
adjustable transverse oscillation frequencies, will allow the study of
superfluidity in variable geometries and dimensionalities.Comment: 4 figures, 10 pages ; the order of the sections has been changed ; to
appear in Phys. Rev.
A cesium gas strongly confined in one dimension : sideband cooling and collisional properties
We study one-dimensional sideband cooling of Cesium atoms strongly confined
in a far-detuned optical lattice. The Lamb-Dicke regime is achieved in the
lattice direction whereas the transverse confinement is much weaker. The
employed sideband cooling method, first studied by Vuletic et al.\cite{Vule98},
uses Raman transitions between Zeeman levels and produces a spin-polarized
sample. We present a detailed study of this cooling method and investigate the
role of elastic collisions in the system. We accumulate of the atoms
in the vibrational ground state of the strongly confined motion, and elastic
collisions cool the transverse motion to a temperature of K=, where is the oscillation
frequency in the strongly confined direction. The sample then approaches the
regime of a quasi-2D cold gas. We analyze the limits of this cooling method and
propose a dynamical change of the trapping potential as a mean of cooling the
atomic sample to still lower temperatures. Measurements of the rate of
thermalization between the weakly and strongly confined degrees of freedom are
compatible with the zero energy scattering resonance observed previously in
weak 3D traps. For the explored temperature range the measurements agree with
recent calculations of quasi-2D collisions\cite{Petr01}. Transparent analytical
models reproduce the expected behavior for and also for where the 2D
features are prominent.Comment: 18 pages, 12 figure
Collective oscillations of a trapped Fermi gas near a Feshbach resonance
The frequencies of the collective oscillations of a harmonically trapped
Fermi gas interacting with large scattering lengths are calculated at zero
temperature using hydrodynamic theory. Different regimes are considered,
including the molecular Bose-Einstein condensate and the unitarity limit for
collisions. We show that the frequency of the radial compressional mode in an
elongated trap exhibits a pronounced non monotonous dependence on the
scattering length, reflecting the role of the interactions in the equation of
state.Comment: 3 pages, including 1 figur
Dynamically Generated Open and Hidden Charm Meson Systems
We will study open and hidden charm scalar meson resonances within two
different models. The first one is a direct application of a chiral Lagrangian
already used to study flavor symmetry breaking in Skyrme models. In another
approach to the problem a SU(4) symmetric Lagrangian is built and the symmetry
is broken down to SU(3) by identifying currents where heavy mesons are
exchanged and suppressing those. Unitarization in couple channels leads to
dynamical generation of resonances in both models, in particular a new hidden
charm resonance with mass 3.7 GeV is predicted. The small differences between
these models and with previous works will be discussed.Comment: 32 pages, 10 figures. Added extra calculations with explicit symmetry
breaking terms in chiral Lagrangian
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