OCV on AHH0001evf
by Whoandwhatitis moderator
Yes, I think you're exactly right. That is likely an off-center vertex near the neutrino(s) (red dashed line). If you switch over to Slice view, you can see that three white lines originate from one point, just beyond the reach of the third layer of the ATLAS detector. Because these particles showed up outside of those inner three detectors, the computers tried to trace the paths back to the beam, and that's why we see three lines that originate horizontally from different locations, but meet at the same place.