update get_events() to require at least 1 nhit trigger to fire

This commit updates get_events() to require at least 1 nhit trigger to fire.
The reason for this is that after looking at a small fraction of the data I
noticed a bunch of instrumental events that weren't getting tagged in run
10141. They looked sort of like neck events and were surrounded by hundreds of
orphaned PMT hits. My best guess is that they really were neck events but the
neck PMT hits and the hits in the lower hemisphere were erroneously not getting
built into the events.

Luckily, all of these events failed the psi cut, but it's not great to rely on
such a high level cut to cut these events. One other thing I noticed was that
these events were triggered mostly by MISS, OWLEL, and OWLEH. Therefore I
thought it might be a good idea to require events to have at least 1 NHIT
trigger. To test whether the NHIT triggers were reliably firing before the
other triggers I looked at all muon events which *didn't* have an NHIT trigger
fire. All of them appeared to be falsely tagged neck events so I'm fairly
confident that the NHIT triggers do reliably fire before the other triggers for
physics events.

1 files changed, 9 insertions, 0 deletions

diff --git a/utils/sddm/plot_energy.py b/utils/sddm/plot_energy.py
index 1971c8d..1a55a85 100755
--- a/utils/sddm/plot_energy.py
+++ b/utils/sddm/plot_energy.py
@@ -33,6 +33,12 @@ MUON_MASS               = 105.6583745   # MeV
 PROTON_MASS             = 938.272081    # MeV
 FINE_STRUCTURE_CONSTANT = 7.297352566417e-3
 
+TRIG_NHIT_100_LO  =      0x00000001
+TRIG_NHIT_100_MED =      0x00000002
+TRIG_NHIT_100_HI  =      0x00000004
+TRIG_NHIT_20      =      0x00000008
+TRIG_NHIT_20_LB   =      0x00000010
+
 def unwrap(p, delta, axis=-1):
     """
     A modified version of np.unwrap() useful for unwrapping the 50 MHz clock.
@@ -558,6 +564,9 @@ def get_events(filenames, merge_fits=False):
     # only need the lower nhit events for neutrons.
     ev = ev[ev.nhit_cal >= 100]
 
+    # Require at least 1 NHIT trigger to fire
+    ev = ev[(ev.trg_type & (TRIG_NHIT_100_LO | TRIG_NHIT_100_MED | TRIG_NHIT_100_HI | TRIG_NHIT_20 | TRIG_NHIT_20_LB)) != 0]
+
     if merge_fits:
         ev = pd.merge(ev,fits,how='left',on=['run','gtid'])
         # Reset n, id1, id2, and id3 columns to integers