Higgs Hunters Talk

Significance of small "Red highlights" dotted around blue outer ring of slice?

  • Black-Dog13 by Black-Dog13

    Does anybody know if the number and position of the red highlights on the outer ring of the slice is of any significance to THIS project? Or are they simply an irrelevant anomaly?


  • Whoandwhatitis by Whoandwhatitis moderator

    The outer ring is the muon calorimeter of the ATLAS detector, and the red highlights that appear are a measure of the energy that is deposited in the detector material. More energetic particles will be marked with larger red highlights. We see in this object that two muons are marked with green lines and medium-sized, thick red highlights just outside of the red ring, extending out into the area of the muon calorimeter.

    Generally, those small red highlights aren't significant when we're classifying objects/pictures. Even the big red ones at the end of the pair of muons aren't interesting in most cases.

    But there are many objects where energy in the muon calorimeter is interesting such as in:

    1. Cosmic ray strikes - Where energetic particles from outside Earth cause a shower of high-energy particles (typically muons) to interact with the detector from the outside-in.
    2. Muon jets - An as-yet unproven phenomenon
    3. Punch-through - Particles decay nearby or within the muon calorimeter, causing an apparent shower of particles.
    4. Excessive amounts of energy or saturation of the muon calorimeter - Sometimes saturation is due to an electrical glitch.
    5. The FAQ also describes some things that you might want to mark:

    Q: What qualifies as "something weird"? - A: @andy.haas: "Lots of tracks in one tight bunch, or coming out at weird angles but not forming a vertex, or a big amount of tracks on one side but the other side, or lots of energy in the calorimeter (the red/green areas beyond the tracker), or things in the muon system (the outermost detector)... what ever looks weird to you!"

    If you're interested in learning more about this:

    The significance of the muon calorimeter in relation to this project is a varied and complex topic, so I don't think I can describe every situation you'll encounter - but that's part of the fun! The discussion in these forums named Blog Entry of Interest has a link to this blog post - the beginning of which shows how collision events at the LHC are selected for permanent storage and thus for projects like this one.

    Have a good time!