6,592 research outputs found
Selected vector-meson decay-distributions in reactions of polarized photons with protons
We develop a formalism for studying vector meson () photo-production at
the proton () with polarized photons, , through an
analysis of the decay distribution in the channel . We show
that this decay distribution differs noticeably from the distributions of
purely hadronic decays, like , .
Formulas for the decay distributions are presented which are suitable for data
analysis and interpretation.Comment: 3 pages, 2 figure
Isoscalar-Isovector Interferences in Reactions as a Probe of Baryon Resonance Dynamics
The isoscalar-isovector () interferences in the exclusive
reactions and near the
threshold leads to a distinct difference of the dielectron invariant mass
distributions depending on beam energy. The strength of this effect is
determined by the coupling of resonances to the nucleon vector-meson channels
and other resonance properties. Therefore, a combined analysis of these
reactions can be used as a tool for determining the baryon resonance dynamics
Metallic proximity effect in ballistic graphene with resonant scatterers
We study the effect of resonant scatterers on the local density of states in
a rectangular graphene setup with metallic leads. We find that the density of
states in a vicinity of the Dirac point acquires a strong position dependence
due to both metallic proximity effect and impurity scattering. This effect may
prevent uniform gating of weakly-doped samples. We also demonstrate that even a
single-atom impurity may essentially alter electronic states at low-doping on
distances of the order of the sample size from the impurity.Comment: 9 pages, 2 figure
May 12 1997 Cme Event: I. a Simplified Model of the Pre-Eruptive Magnetic Structure
A simple model of the coronal magnetic field prior to the CME eruption on May
12 1997 is developed. First, the magnetic field is constructed by superimposing
a large-scale background field and a localized bipolar field to model the
active region (AR) in the current-free approximation. Second, this potential
configuration is quasi-statically sheared by photospheric vortex motions
applied to two flux concentrations of the AR. Third, the resulting force-free
field is then evolved by canceling the photospheric magnetic flux with the help
of an appropriate tangential electric field applied to the central part of the
AR.
To understand the structure of the modeled configuration, we use the field
line mapping technique by generalizing it to spherical geometry. It is
demonstrated that the initial potential configuration contains a hyperbolic
flux tube (HFT) which is a union of two intersecting quasi-separatrix layers.
This HFT provides a partition of the closed magnetic flux between the AR and
the global solar magnetic field. The vortex motions applied to the AR interlock
the field lines in the coronal volume to form additionally two new HFTs pinched
into thin current layers. Reconnection in these current layers helps to
redistribute the magnetic flux and current within the AR in the
flux-cancellation phase. In this phase, a magnetic flux rope is formed together
with a bald patch separatrix surface wrapping around the rope. Other important
implications of the identified structural features of the modeled configuration
are also discussed.Comment: 25 pages, 11 figures, to appear in ApJ 200
Probing nucleon strangeness structure with phi electroproduction
We study the possibility to constrain the hidden strangeness content of the
nucleon by means of the polarization observables in phi meson
electroproduction. We consider the OZI evading direct knockout mechanism that
arises from the non-vanishing s\bar{s} sea quark admixture of the nucleon as
well as the background of the dominant diffractive and the one-boson-exchange
processes. Large sensitivity on the nucleon strangeness are found in several
beam-target and beam-recoil double polarization observables. The small \sqrt{s}
and W region, which is accesible at some of the current high-energy electron
facilities, is found to be the optimal energy region for extracting out the OZI
evasion process.Comment: 8 pages, LaTeX2e, elsart.cls, 3 figures (4 eps files
Diamagnetism of metallic nanoparticles as the result of strong spin-orbit interaction
The magnetic susceptibility of an ensemble of clean metallic nanoparticles is
shown to change from paramagnetic to diamagnetic one with the onset of
spin-orbit interaction. The effect is quantified on the basis of symmetry
analysis with the help of the random matrix theory. In particular, the magnetic
susceptibility is investigated as the function of symmetry breaking parameter
representing magnetic flux in the crossover from symplectic to unitary and from
orthogonal to unitary ensembles. Corresponding analytical and numerical results
provide a qualitative explanation to the experimental data on diamagnetism of
an ensemble of gold nanorods.Comment: 6 pages, 5 figures; extended versio
Ballistic charge transport in chiral-symmetric few-layer graphene
A transfer matrix approach to study ballistic charge transport in few-layer
graphene with chiral-symmetric stacking configurations is developed. We
demonstrate that the chiral symmetry justifies a non-Abelian gauge
transformation at the spectral degeneracy point (zero energy). This
transformation proves the equivalence of zero-energy transport properties of
the multilayer to those of the system of uncoupled monolayers. Similar
transformation can be applied in order to gauge away an arbitrary magnetic
field, weak strain, and hopping disorder in the bulk of the sample. Finally, we
calculate the full-counting statistics at arbitrary energy for different
stacking configurations. The predicted gate-voltage dependence of conductance
and noise can be measured in clean multilayer samples with generic metallic
leads.Comment: 6 pages, 5 figures; EPL published versio
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