Case Study

Suppose we have a file of data called input.dat that we wish to process as follows:-

1. Discard events with less than 10 hits.

2. Output and then discard events with less than 20 hits to small_events.dat

3. Pass the others through the Event Time Fitter (FTT).

4. Output fit failures to fit_fails.dat

5. Output passes to fitted_events.dat

Here are the commands that would achieve this:-

• We start by defining a single input stream and 3 output streams:-

         
  file inp 1 input.dat
  
  file out 1 small_events.dat
  file out 2 fit_fails.dat
  file out 3 fitted_events.dat
  

• Next we define and enable two tests:-
  • Test 1 succeeds if the event has 10 or more hits.

  • Test 2 succeeds if the event has 20 or more hits.

  $define_test 1 $line_1 'nhits float_equals EV+$KEV_NPM: 10 999;'
  $enable_test 1       
  $define_test 2 $line_1 'nhits float_equals EV+$KEV_NPM: 20 999;'
  $enable_test 2
  

• Next we tell Event I/O Support (EIO) that it should use the Programmable Event Loop arguments to define the stream(s) on which to output:-

  $multi_output_sel $pel_args
  

• Now we can define the event loop:-

  define event_loop          *  Start the definition
      call inp               *  Input event
      call flt(1)            *  Apply test 1: PMT hit < 10
      if_not_ok quit_event   *  If it fails we quit this event
      call flt(2)            *  Apply test 2: PMT hit < 20
      if_ok goto big_event   *  If it passes goto big_event
      call out(1)            *  Output event on stream 1
      quit_event             *  and quit
  big_event:                 *  Come here if PMT hit < 20
      call ftt               *  Try to fit
      if_ok goto fit_ok      *  If it passes goto fit_ok
      call out(2)            *  Output fit failures on stream 2
      quit_event             *  and quit 
  fit_ok:                    *  Come here if fit passes.
      call out(3)            *  Output fit passes on stream 3
  end_def                    *  End the definition