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Homework Help: Number of Events Detected (Neutrino Collisions)

  1. Mar 23, 2015 #1
    1. The problem statement, all variables and given/known data
    Hi everyone,

    So I am asked to detect the number of neutrino events that occur from them entering 3000 metric tonnes of pure water. I am given that t=10s , E(neutrino)=10MeV and that the electron cross section is 10^-47 m^2 . This was the famous neutrino experiment at Kamiokande for the explosion of SN 1987a. I also know the neutrino flux on earth due to this event ~ 4x10^13 s^-1m^-2.

    Any help starting off this problem is appreciated!

    2. Relevant equations

    3. The attempt at a solution

    I know I need to find the rate at which electrons are scattered by neutrino collisions in the water . So the reaction is just ν+e-→v+e-.

    I'm guessing that the number of events E detected will be E = collisional frequency * elapsed time

  2. jcsd
  3. Mar 23, 2015 #2


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    How are event rates and cross-sections related?
    Can you calculate the probability that a single electrons takes part in a reaction, and the total number of electrons in the detector?
  4. Mar 23, 2015 #3
    So the number of events will be N = σLt , where σ is the neutrino-electron cross section , L is the integrated luminosity, and t =10s ? The total number of electrons in one molecule of h20 is 10. So in 3,000,000,000g of water we have # electrons = (mass of water * Avogadro's number* 10 electrons) / molar mass of H20
  5. Mar 24, 2015 #4


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    If you take L as integrated luminosity, then it includes the 10 seconds already.
    N is the number of events per electron?
    Looks good.
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