Event 1401: ???

This is a strange event. No ACDs were triggered, which at first glance makes it a gamma-ray candidate. However, the track seems to fizzle out strangely, vanishing from sight before it actually leaves the detector tower. Then significant energy is deposited in the calorimeter, despite the fact that the last few layers of silicon detectors saw nothing go past.

This is where we're showing our limitations as armchair physicists -- we don't know the instrument nearly well enough to say what's going on here. The GLAST designers could probably say at a glance what we're looking at...but that's no fun. So before we cop out and ask the experts, show this event to your own students; maybe they can come up with a good explanation!