Talk:Electron–positron annihilation

message: If a negatron and a positron both have mass, how is it that their annhilation produces two photons that DON'T have mass.
Is it that the photon does have mass OR that the mass is somehow lost during the annihilation OR that the charge of the electrons IS the mass?
I believe that E=mc^2 is responsible - the mass of the converging particles is converted to energy. The mass is fully converted to energy during the annihilation process.
Chris 1127 10:21, 11 January 2006 (UTC)
replies: text: It depends what you mean by "understand".  We have a very good understanding of how elementary particles behave.  For instance, we know their masses, we know which ones interact with which other ones and with what probabilities.  However, I think that it would be a stretch to say that we really know what mass is.  This is too complicated a topic to discuss here.  I suggest that you read up on it on Wikipedia or elsewhere. --Strait 20:18, 2 August 2006 (UTC)
thread_title:  Mass and energy 

message: Can anyone explain how angular momentum is actually conserved if it is conserved at all?  Also, an explanation of why two photons have to be created is needed.--Hpesoj00 14:46, 14 June 2006 (UTC)
replies: text: Angular momentum is conserved.  I have added the explanation you asked for. --Strait 20:18, 2 August 2006 (UTC)
thread_title:  Angular momentum conservation 

message: As is implied by the image, if either the electron or positron has much more energy than the other then they may interact without annihilation. Is this the case? If so, that should be included in the article. --HantaVirus 13:37, 24 July 2006 (UTC)
replies: text: Done. --Strait 20:18, 2 August 2006 (UTC)
thread_title:  e(-) + e(+) that ''doesn't'' yield annihilation? 

message: Conservation laws are not true laws because modern day physicists turn them on and off for various reference frames.  They are better called postulates.  
Even if we accept conservation laws as laws, they do not control nature or the physics of nature.  They are observations of what nature does or does not do, therefore we can not state that the conservation laws define or control anything.  We can say that various processes follow the conservation laws, but we can say that nature is defined by a set of rules or laws that we might envision as explaining what nature does or does not do.  I hope that the members who are helping to write Wikipedia will excercise correct logic in their writing especially in the hard sciences.
Bvcrist 16:51, 2 August 2006 (UTC)
replies: text: You have also posted this in my user talk.  I will reply there. --Strait 20:18, 2 August 2006 (UTC)
thread_title:  Nature can be defined by various laws but is never controlled by them 

message: Does anyone know how the conservation of energy happens in a electron-positron anhilation(creation), also how is the three momentum conserved? --129.108.211.121 
: Well, I'm not sure what you mean by "how", but I'll try to answer the question in the standard manner.  You can always choose a frame in which the total three momentum of the electron and positron is zero.  In this frame, the photons emerge back-to-back with equal energy.  So they also have zero three momentum.  Each photon's energy is equal to the energy of either the electron or the positron, so energy is conserved as well.  Does that answer your question? --Strait 19:00, 23 August 2006 (UTC)
thread_title:  conservation of energy 

message: According to the article for the low energy case, "the gamma rays are emitted in opposite directions". I assume this is relative to the reference frame of the system. However if the system is moving with respect to the observer (i.e. the two particles have a nonzero momentum component perpendicular to the line between their centres), what are the implications for the emitted gamma rays? I assume they won't be moving in exactly opposite directions as far as the observer is concerned, since they will have a component of motion in the direction the electron-positron system was originally moving. Is this true? --202.191.103.123 06:01, 5 September 2007 (UTC)
thread_title:  Linear Momentum Conservation 

message: The second of images is probably wrong.
It shows electron emitting photon on the upper half, and positron emitting photon at the lower half, both changing into something depicted by the straight line between them (what's that? :P)
Here's another image depicting annihilation, also on English Wikipedia:
http://en.wikipedia.org/wiki/Image:Electron-positron-annihilation.svg
and it appears to be right: it shows electron and positron approaching each other, and transformation into a photon in the place of their meeting. Actually there should be two photons, but I saw that image also in my books and in other sites (like this one: http://www.egglescliffe.org.uk/physics/particles/parts/Image14.gif ), so it's probably correct. --sasq777
Both images (the one in question and the one additionally presented here) are incorrect. That said image in question, which is the second on this article, seems to give an undefined, imaginary particle between the electron and positron, with additional electromagnetic interactions which fail to give any product. The other presented image - http://en.wikipedia.org/wiki/Image:Electron-positron-annihilation.svg - is also incorrect, as it presents both the electron and positron with the same charge. Neither give the correct end result, which is a charm and anti-charm. Pastaguy12 (talk) 22:03, 26 March 2013 (UTC)
thread_title:  e<sup>-</sup> + e<sup>+</sup> annihilation, second image wrong 

message: I wonder which fundamental interaction is involved in the electron-positron annihilation. Weak? Thanks, Warut (talk) 17:25, 17 January 2008 (UTC)
replies: text: For annihilation to two photons, it is electromagnetic; that should be clear from its Feynman diagram. The weak interaction would be responsible for annihilation into a Z0 at high energy. 68.34.20.71 (talk) 22:23, 6 December 2009 (UTC)
thread_title:  Fundamental interaction involved 

message: I see no reason to have a special article on electron-positron annihilation any more than muon-antimuon, proton-antiproton, or any other. There is a large amount of overlap and both articles are rather short. 69.140.13.88 (talk) 17:47, 22 December 2009 (UTC)
thread_title:  Merge with [[annihilation]] 

message: It would be nice to have some formulae of the process: the expression of the first order feynmann amplitude, the cross section and its non- relativisic limit... I'm not confident enough to write it myself, though.  — Preceding unsigned comment added by Mcasariego (talk • contribs) 20:11, 7 September 2014 (UTC)
thread_title:  I miss a more technical section... 

message: The redirect Pair Annihilation has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at  until a consensus is reached.  Jason Quinn (talk) 19:46, 27 December 2023 (UTC)
thread_title:  "[[:Pair Annihilation]]" listed at [[Wikipedia:Redirects for discussion|Redirects for discussion]]