The Fork2 Cut

The Fork2 cut is based on logged NCD (signal is negative) signal and is designed to remove fork events which has the second peak smaller than the first peak. This cut is coded as a SNOMAN hard-wired cut "flt_fork2_cut.for". The parameter for this cut are found in "filter_flth.dat" :

*DO   FLTH  31  -i(30I 2I -F)                      #. FLTH: Fork_2 Cut
#.
19750101        0     20380517 03331900   6*0   #.   Standard Database Header
19750101        0     20380517 03331900  16*0
#.
15             #. threshold on the amplitude of second (smaller) peak.
200            #. threshold on the decay time.
0.5            #. threshold on ratio of the amplitudes of second to the first p
eak

There are three parameters for fork2 cut. A event is tagged as fork2 event if

1. the difference between lowest value in the second peak and the highest value between the first and second peak is larger than 15 (or the first parameter in FLTH).
2. it takes less than 200 (or the second parameter in FLTH) ns.
3. The amplitude of the second peak is larger than 0.5 (or the third parameter in FLTH) times the first peak.

To use this cut, one can put a call flt($fork2_cut) in the programmable event loop. The cut returns "true" if the event is a good event.