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Manuscript Title: DWPI: a computer program to calculate the inelastic scattering of pions from nuclei.
Authors: R.A. Eisenstein, G.A. Miller
Program title: DWPI
Catalogue identifier: ABIG_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 11(1976)95
Programming language: Fortran.
Computer: UNIVAC 1108.
Operating system: UNIVAC EXEC II.
RAM: 43K words
Word size: 36
Keywords: Nuclear physics, Scattering, Medium energy, Pion, Distorted wave, Impulse approximation, Angular distribution, Klein-gordon, Cross-section.
Classification: 17.14.

Subprograms used:
Cat Id Title Reference
ABCJ_v1_0 PIRK CPC 8(1974)130

Other versions:
Cat Id Title Reference
AAWD_v1_0 DWPI 2 CPC 16(1979)395

Nature of problem:
Angular distributions for the inelastic scattering of pions are generated using the distorted wave impulse approximation (DWIA). The cross-section for a given transition is calculated by summing a partial wave expansion. The T-matrix elements are calculated using distorted pion waves from the program PIRK, and therefore include elastic scattering to all orders. The excitation is treated in first order only. Several optical potentials and nuclear densities are available in the program. The transition form factor may be uncoupled from the ground state density. Coulomb excitation which interferes coherently with the strong interaction, is a program option.

Solution method:
Angular distributions for the inelastic scattering of pions are generated using the distorted wave impulse approximation (DWIA). The cross section for a given transition is calculated by summing a partial wave expansion. The T-matrix elements are calculated using distorted pion waves from the program PIRK, and therefore include elastic scattering to all orders. The excitation is treated in first order only. Several optical potentials and nuclear densities are available in the program. The transition form factor may be uncoupled from the ground-state density. Coulomb excitation, which interferes coherently with the strong interaction, is a program option.

Restrictions:
A maximum of 30 partial waves (500 mesh points each in the incoming channel can be used without changing the program. The maximum angular momentum transfer is lambda <= 5. The nuclear form factor is from a collective model. The program presently includes only a restricted class of non-local potentials; other types of non-localities may be of physical interest. Typical running time: This depends on the number of partial waves, the number of mesh points, the value of transferred angular momentum lambda, and the ground state spin. The test case given requires 28 s on the Univac 1108 (15 partial waves, 100 integration steps per partial wave, I=0, I'=2).