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Homework Help: Relativistic collisions - different frames, threshold energy

  1. May 27, 2013 #1
    1. The problem statement, all variables and given/known data

    (a) Show that E2 - p2c2 is a Lorentz invariant, where E is the total energy, p is the momentum, c is speed of light.

    (b) In the lab frame, an utlra-relativistic electron with γ = 100 collides head-on with a photon of energy E. Find the threshold energy E required to create an electron-positron pair.

    (c) In another head-on collision with the same setup, the path of the photon is reversed. Find the photon's energy in the electron's rest frame.

    (d) Find the back-scattered energy of the photon in the same frame.

    (e) Find the KE of the electron in the same frame.

    (f) Find the back-scattered energy of photon in LAB frame.


    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. May 29, 2013 #2
    Any help would be very appreciated!
  4. May 29, 2013 #3
    Help would be more forthcoming if you said where it's needed.
  5. May 30, 2013 #4

    Part (d): Is it alright to assume the electron remains stationary throughout the collision (Like a tennis ball rebounding against the wall)

    Part(e): I'm not sure if this is a trick question, but in the elctron's frame, shouldn't it's own KE = 0?
  6. May 31, 2013 #5
  7. Jun 2, 2013 #6
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