1
$\begingroup$

Given

https://www.researchgate.net/publication/323384550_ELECTROWEAK_INTERACTION_AND_ITS_TESTS_Bachelor_Thesis

I wonder why are there two photons entering in a) pair production? Isn't it one photon resulting in $e^+e^-$ ?

|cite|improve this question
$\endgroup$
3
$\begingroup$

It is not possible to satisfy both energy and momentum conservation with only one photon.

|cite|improve this answer
$\endgroup$
  • 1
    $\begingroup$ This is easily seen: For the reverse process, pair annihilation, you can go to the rest frame where the momentum is zero. However, a real photon always moves at the speed of light, there is no rest frame. $\endgroup$ – infinitezero Aug 16 at 12:36
  • $\begingroup$ Right, I remember! :) But another question that arises: When I need a photon that takes a recoil: How/why do the photons interact with each other? Btw, why is a photon resulting in e-e+ in general? :D $\endgroup$ – Ben Aug 16 at 12:37
  • $\begingroup$ @Ben "why is a photon resulting in e-e+ in general?" That probably deserves a fresh question (if it doesn't exist already). $\endgroup$ – PM 2Ring Aug 16 at 12:50

Not the answer you're looking for? Browse other questions tagged or ask your own question.