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Pion decays into gamma rays. Find the energy and angle

  1. Feb 10, 2012 #1
    Hi all,

    I was having trouble with this problem and hoping that someone could help me with it.

    A pion has a rest energy of 135 MeV. It decays into two gamma rays, bursts of electro magnetic radiation that travel at the speed of light. A pion moving through the laboratory at v = 0.97c decays into two gamma rays of equal energies, making equal angles θ with the direction of motion. Find the angle θ and the energies of the two gamma rays. (Hint: gamma rays are electromagnetic radiation with E = pc.)

    I am pretty sure I will be using conservation of relativistic energy and momentum but I am still confused.

    I know that E=γmc^2 and P=γmv

    I find gamma 1/sqrt(1-(0.97c)^2/c^2)≈ 4.11

    I know that mc^2= 135MeV

    With this I get E=(4.11)(135MeV)≈ 555.32MeV

    For P I get (4.11)m(0.97c)=3.99mc≈ 538.66MeV/c

    I am a bit unsure what to do next with this.
  2. jcsd
  3. Feb 10, 2012 #2
    This post should be moved to "Special & General Relativity" subforum. It's a simple exercise in special relativity, and doesn't really require knowledge of particle physics.
  4. Feb 10, 2012 #3
    Boost yourself into the pion's rest frame, then back again afterwards?
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