364 research outputs found
Extension of the generalized multipole technique to three-dimensional anisotropic scatterers
New expansions are derived for the simulation of three-dimensional anisotropic scatterers with the generalized multipole technique (GMT). This extension of the GMT makes possible the investigation of subtle phenomena such as the interaction of light with realistic crystals or magneto-optic materials. (C) 1998 Optical Society of America
Electromagnetic scattering in polarizable backgrounds
We develop a fully vectorial formalism for the investigation of electromagnetic scattering in polarizable backgrounds, i.e., where the scatterers are not in vacuum but situated in a medium with a dielectric permittivity different from unity. Our approach is based on the Green's tensor technique and the corresponding Green's tensors for two-dimensional (2D) and three-dimensional (3D) systems are developed. The analysis of 2D systems is not restricted to the case where transverse electric (TE) and transverse magnetic (TM) modes are decoupled, but treated in a general manner. Practical examples illustrate the application of the method: scattering by a microcavity for two dimensions and color formation in opal for three dimensions
Increasing the performance of the coupled-dipole approximation: A spectral approach
We show that it is possible to increase the performance of the coupled-dipole approximation (CDA) for scattering by using concepts from the sampling theory. In standard CDA, the source in each discretized cell is represented by a point dipole and the corresponding scattered field given by Green's tensor. In the present approach, the source has a certain spatial extension, and the corresponding Green's tensor must be redefined. We derive these so-called filtered Green's tensors for one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) systems, which forms the basis of our new scheme: the filtered coupled-dipole technique (FCD)
Energy flow in light-coupling masks for lensless optical lithography
We illustrate the propagation of light in a new type of coupling mask for lensless optical lithography. Our investigation shows how the different elements comprising such masks contribute to the definition of an optical path that allows the exposure of features in the 100-nm-size range in the photoresist. (C) 1998 Optical Society of Americ
Inclusive Heavy-Flavor Production from Nuclei
We describe a light-cone wave function formulation for hadroproduction of
heavy-flavors at high energies. At moderate values of heavy-flavor
production can be viewed as a diffractive excitation of heavy quark-antiquark
Fock states, present in the interacting gluon from the projectile. The approach
developed here is well suited to address coherence effects in heavy-quark
production from nuclei at small values of x_{t} \lsim 0.1\cdot A^{-1/3}.Comment: 14 pages with 3 figures. To appear in Z. Phys.
Shadowing, Binding and Off-Shell Effects in Nuclear Deep Inelastic Scattering
We present a unified description of nuclear deep inelastic scattering (DIS)
over the whole region of the Bjorken variable. Our approach is based on
a relativistically covariant formalism which uses analytical properties of
quark correlators. In the laboratory frame it naturally incorporates two
mechanisms of DIS: (I) scattering from quarks and antiquarks in the target and
(II) production of quark-antiquark pairs followed by interactions with the
target. We first calculate structure functions of the free nucleon and develop
a model for the quark spectral functions. We show that mechanism (II) is
responsible for the sea quark content of the nucleon while mechanism (I)
governs the valence part of the nucleon structure functions. We find that the
coherent interaction of pairs with nucleons in the nucleus leads to
shadowing at small and discuss this effect in detail. In the large
region DIS takes place mainly on a single nucleon. There we focus on the
derivation of the convolution model. We point out that the off-shell properties
of the bound nucleon structure function give rise to sizable nuclear effects.Comment: 29 pages (and 10 figures available as hard copies from Authors),
REVTE
Peripheral heavy ion collisions as a probe of the nuclear gluon distribution
At high energies a quark-gluon plasma is expected to be formed in heavy ion
collisions at RHIC and LHC. The theoretical description of these processes is
directly associated to a complete knowledge of the details of medium effects in
the nuclear gluon distribution. In this paper we analyze the possibility to
constraint the behavior of this distribution considering peripheral heavy ion
collisions. We reanalyze the photoproduction of heavy quarks for the deduction
of the in-medium gluon distribution using three current parameterizations for
this parton distribution. Moreover, we show that the elastic photoproduction of
vector mesons is a potential process to probe the nuclear gluon distribution.Comment: 8 figures, accepted for publication in Physicsl review
Return of the EMC Effect: Finite Nuclei
A light front formalism for deep inelastic lepton scattering from finite
nuclei is developed. In particular, the nucleon plus momentum distribution and
a finite system analog of the Hugenholtz-van Hove theorem are presented. Using
a relativistic mean field model, numerical results for the plus momentum
distribution and ratio of bound to free nucleon structure functions for Oxygen,
Calcium and Lead are given. We show that we can incorporate light front physics
with excellent accuracy while using easily computed equal time wavefunctions.
Assuming nucleon structure is not modified in-medium we find that the
calculations are not consistent with the binding effect apparent in the data
not only in the magnitude of the effect, but in the dependence on the number of
nucleons.Comment: 11 pages, 6 figure
Nuclear Shadowing in a Parton Recombination Model
Deep inelastic structure functions are investigated in a
rescaling model with parton recombination effects. We find that the model can
explain experimentally measured structure functions reasonably well
in the wide Bjorken range (). In the very small region
(), recombination results are very sensitive to input sea-quark and
gluon distributions.Comment: preprint MKPH-T-93-04, IU/NTC 92-20, 25 pages, TEX file (without
Figs. 1-14)., (address after April 1: Saga U., Japan
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