5 research outputs found
Tunable Graphene Single Electron Transistor
We report electronic transport experiments on a graphene single electron
transistor. The device consists of a graphene island connected to source and
drain electrodes via two narrow graphene constrictions. It is electrostatically
tunable by three lateral graphene gates and an additional back gate. The
tunneling coupling is a strongly nonmonotonic function of gate voltage
indicating the presence of localized states in the barriers. We investigate
energy scales for the tunneling gap, the resonances in the constrictions and
for the Coulomb blockade resonances. From Coulomb diamond measurements in
different device configurations (i.e. barrier configurations) we extract a
charging energy of 3.4 meV and estimate a characteristic energy scale for the
constriction resonances of 10 meV.Comment: 6 pages and 5 figure
reaction in an effective Lagrangian model
We investigate the reaction within an effective
Lagrangian model where the contributions to the amplitudes are taken into
account within the tree level. The initial interaction between the two nucleons
is modeled by the exchange of , , and mesons and
the production proceeds via the excitation of the (1650),
(1710), (1720) baryonic resonances. The parameters of the model at
the nucleon-nucleon-meson vertices are determined by fitting the elastic
nucleon-nucleon scattering with an effective interaction based on the exchange
of these four mesons, while those at the resonance vertices are calculated from
the known decay widths of the resonances as well as the vector meson dominance
model. Available experimental data is described well by this approach. The
one-pion-exchange diagram dominates the production process at both higher and
lower beam energies. The and meson exchanges make negligible
contributions. However, the -exchange processes contribute
substantially to the total cross sections at lower beam energies. The
excitation of the (1710) and (1650) resonances dominate this reaction
at beam momenta above and below 3 GeV/c respectively. The interference among
the amplitudes of various resonance excitation processes is significant. For
beam energies very close to the production threshold the hyperon-proton
final state interaction effects are quite important. The data is selective
about the model used to describe the low energy scattering of the two final
state baryons.Comment: Revised version, to appear in Phys. Rev.