Higgs Hunters Talk

Clarification question

  • PaulMetcalfe by PaulMetcalfe

    If say two lines cross away from the centre and one leads back to the centre but the other does not, can I mark that as a two line vertex with the assumption that the computer assessed that one of those lines would trace back to the centre. Also I (perhaps wrongly) mark two or more crossing lines at their mutual crossing point where none lead back to the centre. Is that okay?




    good question Paul, i'm a volunteer as well....don't know if i ran into that myself.....didn't want u left hang'in...hope u get reply! it's a noble adventure we're in - (after my 2nd day)


  • koranzite by koranzite scientist

    To answer this, let's think about what happens when a vertex is produced. An uncharged (and therefore invisible) particle travels away from the centre. It then decays into two particles, which then spread out in such a way that momentum is conserved before and after the decay. This means that one of the two tracks is going slightly to the left of the direction of the original uncharged particle, and the second is going to the right. If the computer then (mistakenly) traces backwards one of those two paths, it will therefore miss the centre since the charged particles are travelling at an angle to the path of the uncharged parent they decayed from.

    This means that in the case of a line leading back to the centre it likely isn't a vertex. Instead what probably happened is that a charged particle was produced at the centre which then hit something as it traveled outwards, liberating another charged particle and creating the second line.

    TL;DR Two lines crossing when one goes back to the centre probably isn't a vertex. For an example of a vertex where a line goes backwards near (but not exactly towards) the centre, take a look at the 'backward tracks' section of the field guide under classify.

    Hope that helps!



  • PaulMetcalfe by PaulMetcalfe in response to koranzite's comment.

    Thanks Ryan,

    You have made it a lot clearer to me.

    I have previously marked many crossing lines (with some misguided logical thought applied) that I realise now are probably just random lines of some sort.

    So I can now discount any future sightings that I was applying that misguided logic to.

    Thanks again.