The Fork1 Cut

The Fork1 cut is based on logged NCD (signal is negative) signal and is designed to remove fork events which has the first peak smaller than the second peak. This cut is coded as a SNOMAN hard-wired cut "flt_fork1_cut.for". The parameter for this cut are found in "filter_flth.dat" :

*DO   FLTH  30  -i(30I 2I -F)                      #. FLTH: Fork_1 Cut
#.
19750101        0     20380517 03331900   6*0   #.   Standard Database Header
19750101        0     20380517 03331900  16*0
#.
15               #. threshold on the amplitude of first (smaller) peak.
150              #. threshold on the decay time.
0.5              #. threshold on the ratio of the amplitudes of first and second
peak

There are three parameters for fork1 cut. A event is tagged as fork1 event if

1. the difference between lowest value in the first 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 150 (or the second parameter in FLTH) ns.
3. The amplitude of the first peak is larger than 0.5 (or the third parameter in FLTH) times the second peak.

To use this cut, one can put a call flt($fork1_cut) in the programmable event loop. The cut returns "true" if the event is a good event.