Properties of Pions

  • Pions are Mesons
  • There are 3 kinds of Pions: π⁺, π⁻, π⁰
  • Either charged Pion possess a mass of 139.6 MeV and neutral Pion is 135.0 MeV.
  • Pions have spin zero.
  • P+P → π⁺ + n + P
  • P+P → π⁰ + P + P
  • P+n → π⁻ + P + P

  • Charged Pions decay into Muons (Weak Process in Decay):

π⁺ → 𝜇⁺ + 𝜈
π⁻ → 𝜇⁻ + 𝜈

  • The mean life is 2.6 x 10⁻⁸ Sec. 

  • The neutral Pion decays in different way; process is 

π⁰ → 𝛾 + 𝛾 ; This decay is Electromagnetic in nature.

The presence of photons in final state leads us to expect the process is electromagnetic in nature.

The Photons from the decay always seem to come from the spot at which π⁰was produced in some bombardment process. The measurement of life time of such a short lived object is not easy but emulsion techniques provide enough spatial resolution so that in case of rare decay modes

 π⁰ → 𝛾 + 𝛾
π⁰ → 𝛾 + 𝛾 

it is barely possible to measure separation of electrons from place at which  π⁰ was produced.

  •  The mean life of  π⁰ is about 0.89 x 10⁻¹⁶ Sec.

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