100 research outputs found
Microscopic analysis of K^+-nucleus elastic scattering based on K^+N phase shifts
We investigate -nucleus elastic scattering at intermediate energies
within a microscopic optical model approach. To this effect we use the current
-nucleon {\it (KN)} phase shifts from the Center for Nuclear Studies of
the George Washington University as primary input. First, the {\it KN} phase
shifts are used to generate Gel'fand-Levitan-Marchenko real and local inversion
potentials. Secondly, these potentials are supplemented with a short range
complex separable term in such a way that the corresponding unitary and
non-unitary {\it KN} matrices are exactly reproduced. These {\it KN}
potentials allow to calculate all needed on- and off-shell contributions of the
matrix,the driving effective interaction in the full-folding
-nucleus optical model potentials reported here. Elastic scattering of
positive kaons from Li, C, Si and Ca are studied at
beam momenta in the range 400-1000 MeV/{}, leading to a fair description of
most differential and total cross section data. To complete the analysis the
full-folding model, three kinds of simpler calculations are considered
and results discussed. We conclude that conventional medium effects, in
conjunction with a proper representation of the basic {\it KN} interaction are
essential for the description of -nucleus phenomena.Comment: 11 pages, 1 table, 12 figures, submitted to PR
Functional medium-dependence of the nonrelativistic optical model potential
By examining the structure in momentum and coordinate space of a two-body
interaction spherically symmetric in its local coordinate, we demonstrate that
it can be disentangled into two distinctive contributions. One of them is a
medium-independent and momentum-conserving term, whereas the other is
functionally --and exclusively-- proportional to the radial derivative of the
reduced matrix element. As example, this exact result was applied to the
unabridged optical potential in momentum space, leading to an explicit
separation between the medium-free and medium-dependent contributions. The
latter does not depend on the strength of the reduced effective interaction but
only on its variations with respect to the density. The modulation of radial
derivatives of the density enhances the effect in the surface and suppresses it
in the saturated volume. The generality of this result may prove to be useful
for the study of surface-sensitive phenomena.Comment: 11 pages, 5 figures, submitted to Phys. Rev.
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