The QvT cut is intended primarily to cut flashers, particularly those with low charges in the flashing tubes, by cutting events whose maximum charge is many counts above the mean event charge and occurs man nanoseconds earlier than the median event tube time. It is coded as a SNOMAN hard-wired cut, `flt_qvt_cut.for.' The parameters for the cut are found in filter.dat:
*----------------------------------------------------------------------
*DO FLTH 12 -i(33I 6F) #. FLTH: QvT Cut
#.
19750101 0 20380517 03331900 6*0 #. Standard Database Header
19750101 0 20380517 03331900 16*0
#.
1 #. High Gain Charge mode: 1=Use QHL
#. 2=Use QHS
1 #. Cut Mode:1=OR of high and low gain cuts
#. 2=AND of high and low gain cuts
3 #. Time Mode:0=Use only calibrated times
#. 1=If calibrated time of highest
#. charge tube is -9999, then
#. set tube time=to late time
#. boundary if raw time is
#. greater than 2900 ADC counts.
#. 2=Use ECA calibrated data if
#. calibrated time for maximum
#. H or L charges is bad.
#. 3=Use raw TAC data if both PCA and
#. ECA calibrations are bad for
#. either maximum H or maximum L
#. charge.
60. #. Early Time Boundary for QVT cut (nanoseconds
#. relative to median time)
250. #. Late Time Boundary for QVT cut (nanoseconds
#. relative to median time)
500. #. Early Time Boundary for QVT cut (nanoseconds
#. relative to median time), for uncalibrated
#. times
2700. #. Late Time Boundary for QVT cut (nanoseconds
#. relative to median time), for uncalibrated
#. times
1000. #. QHL boundary for QVT cut (relative to average,
#. in pedestal subtracted ADC counts)
180. #. QLX boundary for QVT cut (relative to average)
#. in pedestal subtracted ADC counts)
*------------------------------------------------------------------------
The first three words are the modes with which QvT can be used. The first simply sets which version of the high gain charge (short or long integrate) is considered, and the second specifies whether the high gain and low gain results will be ANDed or ORed (the AND means an event must fail both the high gain and low gain test to be considered bad). The third word deals specifically with the case where a tube time is either lacking calibration or the calibration fails because the tube falls within the TAC `curl' region. If this word is set to 1, then if the maximum charge tube has a bad calibration (-9999) and its raw TAC ADC count is above 2900 ADC counts (the curl region), it is considered an early tube and its time is set to the edge of the Late Time Boundary. For TMODE=2, the cut will default to ECA calibrated data in the case where the maximum charge tube (the one on which the cut will be placed) for either high or low gain has a bad or missing calibration. The third mode, TMODE=3, allows the cut to default to uncalibrated (raw ADC) times if both the ECA and the PCA calibrated times are bad or missing.
The next six words are the cut parameters themselves. The fourth and fifth words, the Early Time Boundary and the Late Time Boundary, specify the box in which tubes are considered early relative to the median tube time--any event which has its maximum charge above the charge boundary and which falls earlier than the Early Time Boundary but later than the Late Time Boundary will be cut. The sixth and seventh words are the same but for uncalibrated (raw ADC) values. The eight and ninth words specify the charge boundaries for both the high gain and low gain charges in units of pedestal subtracted ADC counts. The boundaries are relative to the mean charge in the event.
To use the cut, one can put a call flt($qvt_cut) in the progammable event loop. The cut returns `true' if the event is a good event.