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Homework Help: J/psi meson detection

  1. Dec 11, 2016 #1
    1. The problem statement, all variables and given/known data
    See Image
    The bit about Spectral lines, I couldn't explain why

    2. Relevant equations

    3. The attempt at a solution
    I expected the histogram to peak at the given mass in question and to have a width of about 0.08 MeV calculated as ΔE from the Energy-time uncertainty, but I don't understand how the standard deviation is 52±3 in the CMS graph, this is so far away from my calculation, plus, is this the only difference? I would also suspect that i misunderstood the question maybe. I haven't dealt with such graphs before!

    Attached Files:

  2. jcsd
  3. Dec 12, 2016 #2


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    Staff: Mentor

    If you measure the length of something that is exactly 1.381352413243543 meters long with a ruler, do you expect a result of 1.381352413243543 meters? What would actually happen?

    The same happens in the CMS measurement, just for different reasons because it is not a length measurement.

    The larger width is not the only difference, the shape looks different as well, and there are at least two things you can find (although I'm not sure if the teacher expects those).
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