Talk:Annihilation

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swarm of secondary particle[edit]

"When a proton annihilates an antiproton they produce gamma rays and a swarm of secondary particles, like pairs of top-anti-top quarks."

This seems to be incorrect, or at least misleading, since protons are much too light to create top quarks (the mass of a top quark is similar to that of a Gold nucleus). If the reference is intended to be to high-energy collisions in which the protons and antiprotons carry enough kinetic energy to create a t-tbar pair, this should be explained; in this case, it should also be mentioned that colliding e+-e- pairs can also yield arbitrary kinds of particles (via a highly virtual photon or Z boson).

Possibly Incorrect[edit]

Can someone pleas check to see if and antiparticle and a particle need to be of the same type of in order to annihilate with each other? Thanks! scienceman 23:27, 23 March 2006 (UTC)

They do. Otherwise the sum of their quantum numbers could not be zero. Strait 14:54, 2 June 2006 (UTC)


The feynman diagram where the photon decays into a electron positron pair is somewhat misleading. This can not happen for a free photon (as shown). The reason should be that unlike the W boson or the Z+- it does not have a mass and therefore infinite lifetime.

There is no such diagram on the page. The closest one is the one captioned "A Feynman diagram of a positron and an electron annihilating into a photon which then decays back into a positron and an electron.", which is totally valid. --Strait 17:06, 5 January 2007 (UTC)
There is one problem with that very same Feynmann diagram though - the arrows on the positrons are pointing the wrong way.

Question[edit]

And how close together do they have to be for annihilation to happen?68.6.85.167 10:21, 9 May 2006 (UTC)

Due to quantum uncertainty, such a question may not be meaningful. The probability per unit time will depend on the overlap of the wavefunctions of the two particles. Something on the order of the Compton wavelength, maybe? -- Xerxes 16:22, 9 May 2006 (UTC)

Energy nonconservation?[edit]

What's the deal with this line:

If by intermediate processes in quantum field theory we mean Feynman diagram vertices, then no, every vertex conserves energy. All that's temporarily violated is the energy-momentum relations of free particles. And if we're not talking about Feynman diagrams, then what does this even mean? Melchoir 07:23, 3 July 2006 (UTC)

The Proton-Proton Chain Reaction[edit]

Is it true that the exact reverse of annihilation is involved in the proton-proton chain reaction?--67.10.200.101 00:20, 3 November 2006 (UTC)

I can't see the picture[edit]

I have firefox and I can't see the picture of a positron and an electron annihilating into a photon. I thought I should tell all of you, Jeffrey.Kleykamp 23:22, 12 May 2007 (UTC)

scope[edit]

This article's great, but I feel there should be another article created to discuss NONE physics related annihilation, such as apocalypse. 82.18.44.72 (talk) 23:59, 29 March 2008 (UTC)

Why?[edit]

After much looking, I can't seem to discover the theory behind why antimatter and matter (on contact) annihilate one another. Is it something that is simply unknown, or is it just an omission? 79.71.190.207 (talk) 22:13, 17 February 2009 (UTC)

The particles are simply opposite. They cancel each other out, and… yeah. See the rest of the article for a more detailed background… 24.130.10.143 (talk) 02:48, 21 May 2010 (UTC)

Amount of energy?[edit]

Forgive a non-physicist for lack of knowledge here, but could someone tell me roughly how much energy you get out of particle Annihilation? Hypothetically speaking (particularly in Science Fiction) if a fellow had a heap of Matter and a heap of Anti-Matter and he put the two together, what would he get? Enough power to make his car run, or blow up the earth? If you had an equal mass of, say, Anti-Hydrogen as you did Plutonium, which could you get more energy out of? I know in practice this is pretty much useless to scientists because Anti Matter doesn't just happen to be sitting around in piles, but I've seen it used in Science Fiction and I'm quite curious as to how much energy you get out of it. For that matter, the article could go a section on examples in fiction. 43.244.33.36 (talk) 13:29, 7 March 2009 (UTC)

--The amount of energy released by the anihiliation of matter and antimater is equal to Etotal=mc2+Ekenetic. You take the total mass of the anti-matter and matter which anihilates(this will be equal to twice the mass of the anti-matter, assuming you have less anti-matter than matter), multiply that value by the speed of light squared (the speed of light is 299792458 m/s, so c2=8.98755179 × 1016 m2/s2) and then add the kenetic energy of the anti-matter and matter (this amount is normally negligable, but I add it for completeness.)24.162.159.61 (talk) 15:04, 20 June 2009 (UTC)

Lepton Number not conserved??[edit]

Sorry, but I'm not really knowledgeable in this field. But I came across this when studying for exams :) It states that when an electron and an anti-electron undergo mutual annihilation, the Lepton number does NOT have to be conserved. Thanks for reading! Krazywrath~ (talk) 02:51, 12 May 2009 (UTC)

Article stops short[edit]

The article includes the summary of Electron-positron annihilation taken from the relevant main article, but the summary of Proton antiproton annihilation from its main article is missing. — Preceding unsigned comment added by Rhsimard (talkcontribs) 22:41, 19 March 2011 (UTC)

References?[edit]

I just corrected a factual error (that was introduced and went unnoticed quite some time), but in any case the paragraph on electron-positron annihilation would be a worthwhile target for a rewrite. I find the complete lack of any serious reference even more grave (I myself am not too comfortable in quantum electrodynamics to be able to do that). Seattle Jörg (talk) 13:17, 1 March 2013 (UTC)