INTRODUCTION
Many recent publications have reported studies of
nucleon-nucleus (NA), [1-22] pion-nucleus
(p+,-A), [21-23] and K+
-nucleus (K+A) scatttering (see Refs.
21, 22, and 34-41, and the references cited therein). The methods of theoretical
analysis used in those studies can be divided into two large groups: phenomenological
and microscopic approaches. In the phenomenological approach, besides the
traditional fit of coefficients in the potential (see Refs. 2, 3, 5, 12,
24, 26, 33, 42, and 43), fits are made of parameters in the wave functions
of the scattering states, chosen in analytic form (see Refs. 29, 34, 44,
and 45). This makes it possible to obtain information about the wave functions,
which can be used in the study of nuclear reactions. However, the degree
to which the calculations agree with experiment proves to be somewhat worse
in this case than in the traditional approach involving a fit of parameters
in the potential (see, for example, Ref. 44).
Among the multitude of microscopic approaches (see
Refs. 1, 5 - 8, 10, 12- 24, 27 - 32, and 34 - 41), we can distinguish the
impulse approximation (see Refs. 1, 7, 8, 10,
15- 19, 21, 23, 24, 28, 29, 31, 34-38, 40, and 41) for the construction
of the xA optical potential (x is the incident particle, and A is
the nucleus) as the simplest one. It is widely used at present to describe
pA, p+,- A, and K+A
scattering. The first calculations of pA scattering were performed
at energies below 500 MeV with a potential constructed in the impulse approximation,
in which the partial elementary amplitudes were considered as free parameters
and were obtained from a fit to a pA experiment [46]. At the present
time, a modification of the impulse approximation (involving an analytic
representation of the pN amplitude) is used (see Refs.
1, 8, 10, 15, and 16) to describe pA scattering at energies above
500 MeV, where the calculation reproduces the experimental data satisfactorily.
The application of this method proves to be successful
for the description of the p+,- A
interaction [23-25,28-32] at p -meson energies
Tplab above 100 MeV. In the region
below 100 MeV, a potential with phenomenologically chosen coefficients
works well [24,26,33]. Great success has been achieved in the application
of the impulse approximation in the physics of K+ mesons,
where the available experimental data on K+A elastic
scattering and the total interaction cross section can be described satisfactorily
in this approximation [34-36,40,41].
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