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True width of J/psi particle

  1. Jan 3, 2008 #1


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    I have been reading a bit about the J/psi resonance, and I was wondering about this thing:

    Its true width is relative very small, and all the diagrams I've seen are experimental and they state that the widht in the graph is not the true, but arises due to decetor resolution.

    I was wondering if the cross section at the resonance energy (3097MeV CM-frame in e+e- collision) that is given in my experimental figures (140nb) is the same as the real cross section? The graphs I have states that the integrated cross section is 800nb MeV, but this has nothing do to with the issue I suppose? I am curious how to determine the true width of the J/Psi resonance.

    If the real and experimental cross section is the same ,then one can easy determine the true widht by using Breit-Wigner formula, i can look up the branching ratios at particle data group.

    What I am asking is: Does the dector only make the peak broader, or is it also affecting the hight in a non-neglectable manner?

    EDIT: I found this paper: http://particle.korea.ac.kr/class/2005/phys602/phys602-04.pdf
    But I dont think I understand how the detector changes the peak the way it does, the width I understand, but not the height:/
    Last edited: Jan 4, 2008
  2. jcsd
  3. Jan 4, 2008 #2


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    There is an experimental uncertainty in the beam energy.
    This means that when the central beam energy is at the resonancem peak,
    the measured peak cross-section is a weighted average of the energy spread of the beam.
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