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Why ratio atmospheric ##\nu_\mu : \nu_e = 2:1##

  1. Jul 15, 2015 #1


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    Why is the ratio of atmospheric neutrino fluxes expected to be:
    [itex]R= \frac{\nu_\mu + \bar{\nu}_\mu}{\nu_e +\bar{\nu}_e} =2[/itex]
    for no Neutrino Oscillations?
    An answer that I found gives:
    [itex] \pi \rightarrow \mu \nu_{\mu} \rightarrow e \nu_e \nu_\mu \nu_\mu[/itex]
    But I think this is "wrong" in general, because the muons can reach the Earth before interacting... at least it should be a function of the Zenith angle [itex]\theta[/itex] and their energies (boost).
  2. jcsd
  3. Jul 15, 2015 #2


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    Staff: Mentor

    In general, the spectrum is dominated by low-energetic particles, and low-energetic muons decay in flight.
    You also have some other particles producing muon pairs. That ratio of 2 is only an approximation.
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