Higgs Hunters Talk


  • FrancisHidalgo by FrancisHidalgo

    When the lines form a cross, does it mean that the particles collide?


  • Whoandwhatitis by Whoandwhatitis moderator in response to FrancisHidalgo's comment.

    As far as I know, this can be an error in the calculated path of the two (or more) particles.

    What it looks like in Slice view is that something decayed between the fourth- and fifth- innermost detectors. The computers then tried to map hits in the tracking chamber back to points that appear closer to the beam than where the decay occurred. Essentially, the computer can generate lines where a track doesn't actually exist. This is commonly referred to as backward tracks. This is mentioned briefly in a couple places in the Frequently Asked Questions thread.

    Generally, I'd mark this as an off-center vertex. In Slice view, you see that one curves and goes between the two dark grey detectors, so that hints at a backward track.

    Of course, this won't always be the case, but mark it as you see fit, especially since you're not given multiple views when classifying objects.


  • peterwatkins by peterwatkins scientist

    In most cases where lines cross they are separated from each other at the crossing point so they do not collide.
    With the two dimensional views we use in these images the positions of the two lines in the third (unseen) direction cannot be deduced.

    If two lines appear to start at the same point on an image then it is more likely that they are at the same point in space but this can only be confirmed by using more than one view of the collision.


  • Whoandwhatitis by Whoandwhatitis moderator in response to peterwatkins's comment.

    Thank you Peter. Given that, I think it would be accurate to not mark this type of crossing as an off-center vertex. Always nice to learn a bit more!