The In-Time Channel (ITC) time spread cut

This is a time spread cut based on the PMT hit times that is independent of the PMT geometry (unlike the FTS_CUT). The cut exploits the fact that events due to Cerenkov light have most of their PMT hits ``in-time'' - i.e. within the transit time of light across the detector of each other. The algorithm is to slide a time window of fixed size around the event TAC spectrum and use as the cut statistic the ratio of the max number of hits in any window to the total number of (calibrated) hits in the event. ``Good'' events are expected to have ratio close to one for an appropriate sized window, so the cut fails events having too small of an in-time channel ratio.

The input parameters used in the ITC cut are the following:

• WINSIZE - The width (in ns) of the sliding window used to count the number of in-time channels.
• WINSTEP - Step size (in ns) used in incrementing the window position between the limits of the event TAC spectrum.
• RAT_CUT - The ITC cut statistic. Events are passed if the ratio of the max number of hits in any window to the total number of (calibrated) hits in the event is greater than RAT_CUT.

The cut parameters previously described which can be adjusted are contained in the titles file filter.dat, the relevant part of which is shown below:

*DO   FLTH  23  -i(30I -F)            #.  FLTH: In-Time Channel time spread cut
#.
19750101        0 20380517 03331900   6*0   #.   Standard Database Header
19750101        0 20380517 03331900  16*0
#.
93.                          #. Sliding window size (in ns)
1.                           #. Step (in ns) of sliding window
0.6                          #. Cut value for in-time ratio