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Manuscript Title: A Monte Carlo reaction simulation for small-angle correlations between light charged particles.
Authors: R.L. McGrath, A. Elmaani, J.M. Alexander, P.A. DeYoung, T. Ethvignot, M.S. Gordon, E. Renshaw
Program title: KALLIOPI
Catalogue identifier: ABRU_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 59(1990)507
Programming language: Fortran.
Computer: IBM 3090-600E.
Operating system: VMS 4.5, VM/CMS, VM/XA.
RAM: 102K words
Word size: 32
Keywords: Nuclear physics, Reactions nuclear, Nucleus compound Lifetimes, Small-angle correlations, Particle evaporation, Monte carlo method, Simulation, Heavy ion.
Classification: 17.7.

Nature of problem:
If two charged particles are emitted from the same compound nucleus within a short time interval (e.g. <10**-20s), then they may experience observable final-state interactions. The strength of these interactions is related to the size and lifetime (space-time extent) of the emitter. This program simulates the particle-particle correlations to be expected if the emitter lifetime is long enough (>/=10**-22s) to dominate the effective space-time extent of the source. One measures the correlations between particles by detector pairs with small separation angles. The comparison of these small-angle correlations to Monte Carlo trajectory simualtions can be used to determine the lifetimes of the emitting nuclei. In this way one can explore the very interesting time region of 10**-22 to 10**-20s.

Solution method:
The Monte Carlo method is used.

Restrictions:
The logic of the program is straightforward. However, the user must be careful to restrict the angular regions for particle emission. If these restrictions are too generous, then a great deal of computer time can be wasted. If these restrictions are too tight, then the results can be biased.

Unusual features:
This simulation can be used in three ways: Option (1) One can assume that the time interval between the successive emission of two particles is given by an expotential decay law. Then he can use the mean lifetime as a parameter to be varied to fit experimental data. Option (2) One can use the statistical model (external to this program) to predict various aspects concerning the sequence of emitted particles. Then he can provide this information as program input to be used to calculate mean lifetimes for each evaporation step and subsequently the observable correlations. Option (3) One can use an even more detailed statistical model (external to the program) to predict the mean lifetimes, emission probabilities and spectral shapes for each particle at each step. With these input mean lifetimes, etc. he can predict the observable correlations. By using options (2 or 3) one can test statistical model predictions at his own chosen level of sophistication. With option (1) he can obtain an empirical mean lifetime independent of the principle of detailed balancing as used in current statistical models. The program provides for a detector array of M by N cells.

Running time:
4466m CPU for VAX 780; 277m for the IBM 3083; 118m for IBM 3090-600E for the input deck given.