What is the status of the 'x' type marking in the lower right quadrant?
by Whoandwhatitis moderator
Typically these 'X' patterns aren't an off-center vertex. This could be the result of particles colliding with detector material, which happens pretty frequently.
However, with backward tracks, you might see an 'X' pattern. This happens when the computers go overboard and they draw non-existent paths back toward the beam-line. From the FAQ:
Q: Are all line crossings OCVs? - A: No. Remember that we are looking
at a 2d representation of a 3d picture (+time). Sometimes the paths of
some particles just seem to cross in one of the views. Use your own
judgement and don't worry, if it's unclear in one view the data for
the other view will make up for it!