1,505 research outputs found
Wave function engineering in quantum dot-ring nanostructures
Modern nanotechnology allows producing, depending on application, various
quantum nanostructures with the desired properties. These properties are
strongly influenced by the confinement potential which can be modified, e.g.,
by electrical gating. In this paper we analyze a nanostructure composed of a
quantum dot surrounded by a quantum ring. We show that depending on the details
of the confining potential the electron wave functions can be located in
different parts of the structure. Since the properties of such a nanostructure
strongly depend on the distribution of the wave functions, varying the applied
gate voltage one can easily control them. In particular, we illustrate the high
controllability of the nanostructure by demonstrating how its coherent,
optical, and conducting properties can be drastically changed by a small
modification of the confining potential.Comment: 8 pages, 10 figures, 2 tables, revte
How Universal Is the Relationship Between Remotely Sensed Vegetation Indices (VI) and Crop Leaf Area Index (LAI)?
Global LAI-VI relationships are statistically significant, crop-specific, and mostly non-linear. This research enables the operationalization of large-area crop modeling and, by extension, has relevance to both fundamental and applied agroecosystem research
Entanglement of qubits via a nonlinear resonator
Coherent coupling of two qubits mediated by a nonlinear resonator is studied.
It is shown that the amount of entanglement accessible in the evolution depends
both on the strength of nonlinearity in the Hamiltonian of the resonator and on
the initial preparation of the system. The created entanglement survives in the
presence of decoherence.Comment: 6 pages, 10 figure
Total and Differential Cross Sections for the pp-->pp eta-prime Reaction Near Threshold
The eta-prime meson production in the reaction pp-->pp eta-prime has been
studied at excess energies of Q = 26.5, 32.5 and 46.6 MeV using the internal
beam facility COSY-11 at the cooler synchrotron COSY. The total cross sections
as well as one angular distribution for the highest Q-value are presented. The
excitation function of the near threshold data can be described by a pure
s-wave phase space distribution with the inclusion of the proton-proton final
state interaction and Coulomb effects. The obtained angular distribution of the
eta-prime mesons is also consistent with pure s-wave production.Comment: 6 pages, 5 figures, submitted to Eur. Phys. J.
Production of Eta Mesons in Proton-Proton Collisions Close to Threshold
A brief experimental overview on the close-to-threshold eta meson production
in proton-proton interactions is presented and the available observables in
measurements with unpolarized and polarized beam and target are discussed.Comment: 4 pages; Presented at Meson 2004: 8th International Workshop on Meson
Production, Properties and Interaction, Krakow, Poland, 4-8 June 2004;
Submitted to International Journal of Modern Physics
Isospin dependence of the eta' meson production in nucleon--nucleon collisions
According to the quark model, the masses of eta and eta' mesons should be
almost equal. However, the empirical values of these masses differ by more than
the factor of two. Similarly, though the almost the same quark-antiquark
content, the total cross section for the creation of these mesons close to the
kinematical thresholds in the pp --> ppX reaction differs significantly. Using
the COSY-11 detection setup we intend to determine whether this difference will
also be so significant in the case of the production of these mesons in the
proton-neutron scattering. Additionally, the comparison of the pp --> pp eta'
and pn --> pn eta' total cross sections will allow to learn about the
production of the eta' meson in the channels of isospin I = 0 and I = 1 and to
investigate aspects of the gluonium component of the eta' meson.Comment: Presented at LEAP05: International conference on Low Energy
Antiproton Physics, Bonn - Juelich, Germany, May 16-22, 200
General thoughts to the Kaon pair production in the threshold region
Simple--minded thoughts about the cross sections for the reactions
pp-->ppK+K- and pp-->ppK0K0 are presented, which certainly do not account for
the complex coupled channel problem but rather provide some ideas into the
mutual reaction dynamics.Comment: Talk given at 9th International Workshop on Meson Production,
Properties and Interaction, Cracow, Poland, 9-13 June 2006. 3 pages, 2
figure
COSY-11: an experimental facility for studying meson production in free and quasi-free nucleon-nucleon collisions
The COSY-11 experimental setup is an internal facility installed at the
COoler SYnchrotron COSY in Juelich. It allows to investigate meson production
in free and quasi-free nucleon-nucleon collisions, eg. pp --> pp meson and pd
--> p_sp np meson reactions. Drift chambers and scintillators permit to measure
outgoing protons, separated in magnetic field of COSY-11 dipole. Neutrons are
registered in the neutron modular detector installed downstream the beam.
Recently, the experimental setup has been extended with spectator detector,
deuteron drift chamber and polarization monitoring system, and since then meson
production can be investigated also as a function of spin and isospin of
colliding nucleons.Comment: Presented at LEAP05: International conference on Low Energy
Antiproton Physics, Bonn - Juelich, Germany, May 16-22, 200
Associated strangeness production in pp collisions near threshold
Motivated by the ongoing discussion concerning the nature of the scalar
resonances f0(980) and a0(980), the COSY-11 collaboration has taken exclusive
data on the pp->ppK+K- reaction near the production threshold. A first total
cross section sigma=(1.80+-0.27+0.28-0.35)nb for the excess energy Q=17 MeV has
been determined. In contrary to the eta, omega and eta' single meson production
studies which clearly show the strong pp final state interaction (FSI), the
cross section values obtained at COSY-11 and DISTO can be both described by a
fit with a four-body phase space including the proton-proton final state
interaction as well as with one-meson exchange calculations neglecting FSI
effects. Therefore, one might think about a compensation of the strong pp
interaction through a pK- FSI effect or an additional degree of freedom caused
by the four-body final state. In the latter case, strong FSI effects can be
expected at Q-values very close to the K+K- production threshold. Such a
motivation triggered -- in combination with the investigation of the
kaon-Antikaon interaction being relevant to the structure of the f0(980) --
further measurements at the excess energies Q=10 and Q=28 MeV at COSY-11.Comment: 5 pages, 4 figures, Presented at X. International Conference On
Hadron Spectroscopy (Hadron 2003), Aschaffenburg, Germany, 31 Aug - 6 Sep
200
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