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Cosmic rays affecting the LHC

  1. Jul 23, 2013 #1
    I've heard of cosmic rays affecting measurements made at the LHC in the context of muons. Is it just muons that can reach the detectors or is there background from other particles as well? Why are muons a background but not electrons? How significant is it?

  2. jcsd
  3. Jul 23, 2013 #2


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    Muons have a longer range than electrons, however I don't see how cosmic ray muons could be responsible for a significant background in the LHC, since the detectors by design are very sensitive to direction and time of arrival.

    However there was a period before the LHC was fully operational in which data from cosmic rays was used to test the detectors efficiency.
    Last edited: Jul 23, 2013
  4. Jul 23, 2013 #3


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    The rate of cosmic muons is low compared to the rate of muons from the collisions, and muons produced in the LHC mainly come from the small interaction region, while cosmic muons travel in random directions.

    Muons are heavier than electrons, so they lose less energy in matter. In addition, pion decays in the upper atmosphere mainly produce muons, not electrons.
    Well, neutrinos can reach them, too, but they are not an issue as their reaction probability is so tiny.

    Cosmic muons are nice to align the detector elements before the first collisions are available - they go in a straight line, and you can see which detector elements are hit and find out where they are based on that.
  5. Jul 23, 2013 #4
    Thanks to you both!
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