SR: Gamma rays creating election-positron pair

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SUMMARY

The discussion centers on the impossibility of positron-electron pair creation from two gamma rays colliding at an angle of zero (\theta=0) in the context of special relativity. It is established that for pair creation to occur, the energy of the gamma rays must exceed the rest mass energy of the electron and positron, and the conservation of momentum must be maintained. The participants explore the implications of momentum conservation, concluding that at \theta=0, the necessary conditions for pair creation are not met.

PREREQUISITES
  • Understanding of special relativity principles
  • Knowledge of photon energy and rest mass energy concepts
  • Familiarity with momentum conservation laws
  • Basic grasp of particle physics, specifically electron-positron pair production
NEXT STEPS
  • Study the conditions for photon collisions leading to particle creation
  • Learn about the role of momentum conservation in high-energy physics
  • Investigate the implications of different collision angles on particle production
  • Explore the concept of center-of-mass frames in particle interactions
USEFUL FOR

Students and educators in physics, particularly those focusing on particle physics and special relativity, as well as researchers exploring high-energy photon interactions.

villiami
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Homework Statement



This is a special relativity question: Two gamma rays of identical energies E collide with an angle \theta between their velocities. Show that positron-electron pair creation is impossible in the limiting case \theta=0.

Find the minimum \theta value for p-e creation to the possible.

The Attempt at a Solution


Stuck! If E is greater than election rest mass, can't it happen at any angle?
 
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Is it possibly that: with photons, there are no frames in which momentum=0.
If the p-e pair were produced, there will then be a frame in which momentum=0 (which previously had non-zero momentum photons).
Thus mom is not conserved?
 

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