README trig_filter_treeX for bcal06 data
May 5, 2008

This directory contains 3 programs that are near identical
copies of one another. There are 3 different ones corresponding
to 3 different versions of the bcal TTree definition used
in producing the bcal_dst files in /work/halld/bcal06 on the
JLab CUE.

The purpose of these programs is to read in events from root
files produced by bcal_dst and write only the events satisfying
a trigger mask into an output file. The output tree is of
the same format as the input tree, except that the run number
is added as another branch.

The programs were written specifically to address a request
by the Regina group to have a set of files containing only
cosmic triggers. This is useful for production runs which
had cosmic data sprinkled in amongst a sea of beam photon
events making it uneseccarily long to make a single pass.

The programs are all run with 2 arguments. The first is an
integer representing the bit pattern of the triggers one
wishes to keep and the second is the input file name. For
example:

trig_filter_tree1 32 bcal_dst02371.root

This would create a file called bcal_dst02371_t6.root that
had only events in which trigger 6 (=log(32)/log(2)+1) was
set. Note that other triggers could be present as well.

The program of the appropriate tree type should be used.
If one uses the trig_filter_tree2 program on a bcal_dst
file containing a "version 1" tree, then a seg fault is
likely and the desired result will not be achieved. Lists
of which files belong to each type can be found in the
following files:

/work/halld/bcal06/tree1files.txt
/work/halld/bcal06/tree2files.txt
/work/halld/bcal06/tree3files.txt


Please direct any questions or comments to David Lawrence
at davidl@jlab.org.