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Pair Production

by Claire84
Tags: pair, production
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Claire84
#1
Dec21-03, 06:17 PM
P: 221
I'm pretty much okay with pair production but in the eqt we have that a photo gives an electron and a positron. If we do it the other way round we have an electron and a positron giving 2 photos in order to conserve momentum. Why do we not have 2 photos of energy for pair production ir order to conserve momentum?
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mathman
#2
Dec21-03, 07:40 PM
Sci Advisor
P: 6,070
You are correct (up to a point). Pair production in a vacuum does require two photons to interact. However, when a high energy photon passes near a nucleus of an atom (the heavier the better), it can give rise to pair production alone, with the nucleus taking care of the momentum balance.
Claire84
#3
Dec22-03, 03:20 PM
P: 221
Is that to do with the recoil momentum of the nucleus? I've heard it mentioned before so just wondering if that's what is going on here.

mathman
#4
Dec22-03, 07:06 PM
Sci Advisor
P: 6,070
Pair Production

Your description is correct. It also explains why heavier nuclei are better. It is easier for them to absorb the recoil momentum.


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