7 research outputs found
Nuclear dependence of the coherent eta photoproduction reaction in a relativistic approach
We study the nuclear (or A) dependence of the coherent eta photoproduction
reaction in a relativistic impulse approximation approach. We use a standard
relativistic parameterization of the elementary amplitude, based on a set of
four Lorentz- and gauge-invariant amplitudes, to calculate the coherent
production cross section from He-4, C-12, and Ca-40. In contrast to
nonrelativistic treatments, our approach maintains the full relativistic
structure of the process. The nuclear structure affects the process through the
ground-state tensor density. This density is sensitive to relativistic effects
and depends on A in a different manner than the vector density used in
nonrelativistic approaches. This peculiar dependence results in He-4 having a
cross section significantly smaller than that of C-12---in contrast to existent
nonrelativistic calculations. Distortion effects are incorporated through an
eta-nucleus optical potential that is computed in a simple ``t rho''
approximation.Comment: 4 pages, 3 postscript figures. The replace is due to a misspelling in
the Authors' lis
The -3N problem with separable interactions
The -3N-interaction is studied within the four-body Faddeev-Yakubovsky
theory adopting purely separable forms for the two- and three-body
subamplitudes, limiting the basic two-body interactions to s-waves only. The
corresponding separable approximation for the integral kernels is obtained by
using the Hilbert-Schmidt procedure. Results are presented for the -H
scattering amplitude and for the total elastic cross section for energies below
the triton break-up threshold.Comment: revised version accepted for Phys. Rev. C, 16 pages revtex including
6 eps-figures, formal part shortene