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Charged pion decay in to Tau

  1. Dec 16, 2014 #1
    This may be a silly question, but what prevents the decay of a Pion in to a (anti) Tau and (anti)Tau neutrino. I can see the process for the electron but not for the tau.
  2. jcsd
  3. Dec 16, 2014 #2


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    Conservation of energy. The tau lepton is heavier than the pion.
  4. Dec 16, 2014 #3


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    In the CM of the pion, it will have [itex]E = m_\pi \approx 135 ~MeV[/itex]
    Then decaying to something that needs at least (for its mass purposes) energy of [itex]E \sim M_\tau \approx 1777 ~MeV [/itex] is impossible.
    That's something one has to check everytime he has a decay of the form : [itex] X \rightarrow A_1 + A_2 + ... +A_n [/itex]
    That's not though the case of [itex] X+Y \rightarrow N- \text{particles}[/itex]
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