CRAB 3.0alpha

November 17, 1997

Scott Pratt
National Superconducting Cyclotron Laboratory
Michigan State University, East Lansing, MI  48824
pratt@nscl.msu.edu (517) 333-6438

CRAB stands for ``Correlation After Burner''. It is a set of codes used to
generate correlation codes from semi-classical transport codes. It reads files
of phase space points, which describe the final momentum and point of last
interaction of generated particles. From this information, along with knowledge
of the impact parameters used for the transport-code runs, CRAB will generate
correlation functions which account for impact-parameter averaging,
experimental acceptances, experimental resolution and kinematic cuts. 

CRAB can implement full quantum corrections for Coulomb interactions between
the two particles as well as strong interactions for an arbitrary number of
partial waves. There is also an option to include interactions of a
Breit-Wigner form.  CRAB does not account for strong interactions that mix
partial waves or for interactions with third bodies, e.g. interacting with the
residue of a compound nucleus.

Version 3.0 is completely rewritten in C++, but shares a great deal of
philosophy with the previous FORTRAN version. Differences with previous
versions are summarized below:

1. Different momentum binnings can be incorporated in the same run. For
example, if one wishes to perform cuts in pt and rapidity at the same time you
perform calculations for Qinv, it is straight-forward to implement. One can
perform an arbitrary number of binnings in the same run.

2. The mesh used for calculating strong-interaction corrections to partial
waves can be as fine as one wishes and is not tied to the resolution of the
meshes used for binning.

3. Three-dimensional binnings can be incorporated.

4. It is easier to change the interaction between particles as parameters
that define the interaction reside in one short file.

5. Phase space pt.s can be read from a file which contains information about
all emitted particles, even those that are not considered in the correlation
analyses. One can set which kinds of particles are used for the analyses. For
instance, one may wish to include phase space pt.s for pi^+, pi^- and
pi^0 for greater statistics, even though only negative pions are truly being
considered. The default input format is OSCAR 1997A.

6. Estimates of statistical errors accompany the calculation.

Although previous versions were easy to use, they were not easy to modify. The
new version was designed with the intention of making it easy for the user to
modify rather than just making it easy to run.

See the file 'updates.txt' for information about additions and error fixes. A
detailed description of the code and directions can be found in the file
'documentation/crab.ps'.
