Event 1416: a low-energy cosmic ray?

This event triggered two ACDs (the black rectangles shown above the detector tower), so it probably represents a charged particle, not a gamma ray. It seems to be a low-energy particle, both because it deposited very little energy in the calorimeter at the end of its flight (though it looks like part of the shower may have missed the calorimeter altogether), and because several of the daughter particles it produces are moving in noticably different directions from their parent.

There's one odd note here: one of the ACDs which was triggered lies in the path of the particle, but the other one does not. This was likely due to some sort of "splash" effect, in which some of the daughter particles produced in the first ACD or the top layer of the detector skipped across the instrument to land in the opposite ACD.