218,028 research outputs found
Rectifying "nanohomo" contacts of W-Ga-C composite pad and nanowire fabricated by focused-ion-beam induced chemical vapour deposition
We prepared W-Ga-C composite contacts on W-Ga-C composite nanowires by focused-ion-beam-induced chemical vapor deposition using a dual-beam scanning electron microscope/focused-ion-beam system. The current-voltage (I-V) characteristics of wires were found to change from nonlinear to linear with increasing wire thickness. For wires with small dimensions, which result in strong nonlinear I-V behavior at room temperature, pairs of contacts were fabricated along the wire under different ion energies and scanning modes. Nonlinear and asymmetric rectifying I-V characteristics were observed. The results suggest that nanoscaled W-Ga-C nanowires may behave similarly to semiconductors and that the contact characteristics may be modified using different deposition conditions. Furthermore, ohmiclike junctions could be formed through the use of specific deposition conditions for the contact pads and nanowires
Photoproduction of Pentaquark in Feynman and Regge Theories
Photoproduction of the Theta+ pentaquark on the proton is analyzed by using
an isobar and a Regge models. The difference in the calculated total cross
section is found to be more than two orders of magnitude for a hadronic form
factor cut-off Lambda > 1 GeV. Comparable results would be obtained for 0.6 <
Lambda < 0.8 GeV. We also calculate contribution of the Theta+ photoproduction
to the GDH integral. By comparing with the current phenomenological
calculation, it is found that the GDH sum rule favors the result obtained from
Regge approach and isobar model with small Lambda.Comment: 5 pages, 5 figures, submitted to Phys.Rev.C as a Rapid Communicatio
Meson Emission Model of Psi to N Nbar m Charmonium Strong Decays
In this paper we consider a sequential "meson emission" mechanism for
charmonium decays of the type Psi -> N Nbar m, where Psi is a generic
charmonium state, N is a nucleon and m is a light meson. This decay mechanism,
which may not be dominant in general, assumes that an NNbar pair is created
during charmonium annihilation, and the light meson m is emitted from the
outgoing nucleon or antinucleon line. A straightforward generalization of this
model can incorporate intermediate N* resonances. We derive Dalitz plot event
densities for the cases Psi = eta_c, J/psi, chi_c0, chi_c1} and psi' and m =
pi0, f0 and omega (and implicitly, any 0^{-+}, 0^{++} or 1^{--} final light
meson). It may be possible to separate the contribution of this decay mechanism
to the full decay amplitude through characteristic event densities. For the
decay subset Psi -> p pbar pi0 the two model parameters are known, so we are
able to predict absolute numerical partial widths for Gamma(Psi -> p pbar pi0).
In the specific case J/psi -> p pbar pi0 the predicted partial width and M_{p
pi0} event distribution are intriguingly close to experiment. We also consider
the possibility of scalar meson and glueball searches in Psi -> p pbar f0. If
the meson emission contributions to Psi -> N Nbar m decays can be isolated and
quantified, they can be used to estimate meson-nucleon strong couplings
{g_NNm}, which are typically poorly known, and are a crucial input in meson
exchange models of the NN interaction. The determination of g_NNpi from J\psi
-> p pbar pi0 and the (poorly known) g_NNomega and the anomalous "strong
magnetic" coupling kappa_{NNomega} from J/psi -> p pbar omega are considered as
examples.Comment: 10 pages, 5 figure
Constraint on intermediate-range gravity from earth-satellite and lunar orbiter measurements, and lunar laser ranging
In the experimental tests of gravity, there have been considerable interests
in the possibility of intermediate-range gravity. In this paper, we use the
earth-satellite measurement of earth gravity, the lunar orbiter measurement of
lunar gravity, and lunar laser ranging measurement to constrain the
intermediate-range gravity from lambda=1.2*10^{7}m - 3.8*10^{8}m. The limits
for this range are alpha=10^{-8}-5*10^{-8}, which improve previous limits by
about one order of magnitude in the range lambda=1.2*10^{7}m-3.8*10^{8}m.Comment: 8 pages, International Journal of Modern Physics D, in press (World
Scientific, 2005
Interdot Coulomb repulsion effect on the charge transport of parallel double single electron transistors
The charge transport behaviors of parallel double single electron transistors
(SETs) are investigated by the Anderson model with two impurity levels. The
nonequilibrium Keldysh Green's technique is used to calculate the
current-voltage characteristics of system. For SETs implemented by quantum dots
(QDs) embedded into a thin layer, the interdot Coulomb repulsion is
more important than the interdot electron hopping as a result of high potential
barrier height between QDs and . We found that the interdot Coulomb
repulsion not onlyleads to new resonant levels, but also creates negative
differential conductances.Comment: 12 pages, 7 figure
Fluctuation limits of strongly degenerate branching systems
Functional limit theorems for scaled fluctuations of occupation time
processes of a sequence of critical branching particle systems in with
anisotropic space motions and strongly degenerated splitting abilities are
proved in the cases of critical and intermediate dimensions. The results show
that the limit processes are constant measure-valued Wienner processes with
degenerated temporal and simple spatial structures.Comment: 15 page
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