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kryptonite

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Oct 29, 2005
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Ive got a question. Ive been reading about antimatter alot lately and have been interested in it. I read that gamma ray photons are produced in annihilation but read where one dude stated pions are produced, not gamma rays. I want to know if this is true and what the heck pions are. On wikipedia it said pions are subatomic particles that are their own antiparticle or some stuff like that. My question is, what are pions and what exactly is produced in antimatter-matter annihilation? Is any form of matter at all produced in annihilation? Because I thought annihilation is where antimatter and matter come together to make pure energy and nothing else.
thanks
 
Any peon is annihilated if he doesn't pick enough sugar cane ! Anyway that's how a metallurgist sees it !
 
I can ASSURE you with ABSOLUTE CERTAINTY that the annihilation reaction which occurs when a positron and electron interact at low kinetic energies, that the resultant product of the reaction in 2 diametrically opposed coincident 511 keV photons. If that was not the case I wouldn't have a whole helluva lot to do on Monday mornings!:cool: I also would have MUCH less money to spend on knives!:eek: If my physics recall is right I believe you get a neutrino out of the deal as well, which would make sense given the conservation of mass. Sorry...yep...I was right 2 511 keV photons and a neutrino.
 
I read something about that but it was a while ago and it was complicated. It's not as simple as proton + antiproton = gamma ray -- there's a whole series of reactions with matter/antimatter turning to energy but the energy is so concentrated it turns into smaller particles and antiparticles and although they tend to mutually annihilate again that doesn't happen instantly (not in the timescale of nuclear reactions) and according to the article I read it would be possible to extract some of the energy in more usable forms than hard gamma.

There must be a better place to ask that question, somewhere on the net....
 
Of course marcangel is right; when an electron and positron annihilate that's very simple, as there are no particle/antiparticle pairs of lower energy for the energy released to create. It's when you start playing with protons & antiprotons that things get complicated.
 
That must be why Venkman and Spengler avoided crossing the streams. :D
 
Kryptonite,

Here's a link that describes high energy electron-positron collisions http://www.physorg.com/news73669760.html , and the current or a recent issue of Scientific American describes what happens at the Relativistic Heavy Ion Collider where they smash gold nuclei together at near the speed of light. The Large Hadron Collider is in the works and may be powerful enough to reach densities that will create microscopic black holes that "should" quickly evaporate.
 
kryptonite said:
Alright, thanks yall. But one thing, is a neutrino matter?
Click to expand...

Yes. Kinda. Pretty much. A neutrino DOES have mass. For a long time we didn't think so, because it passes through alot of matter nearly unhindered, but since it has mass, it is matter.

BTW, what Cougar said in his first discussion was also correct, there are a whole boatload of reactions that cascade at the sub-atomic particle level that occur VERY quickly. Unfortunately, for the purposes of this discussion I really only care about the medical implications of these reactions (medical physics) and really am not at all versed in the really nitty-gritty stuff so I bow to those of you with backgrounds in sub-atomic particle physics. I draw the line at the neutrino...:o
 
Last I heard that idea that neutrinos might have mass had been pretty thoroughly refuted. Although of course it is forever impossible to prove the mass is exactly zero, it's been proven to be less than an extremely small amount, which so far has kept getting smaller as measurements are refined.
 
From Wikipedia

The neutrino is an elementary particle. It has half-integer spin () and is therefore a fermion. All neutrinos observed to date have left-handed chirality. Although they had been considered massless for many years, recent experiments (see Super-Kamiokande, Sudbury Neutrino Observatory, KamLAND and MINOS) have shown their mass to be non-zero. Because it is an electrically neutral lepton, the neutrino interacts neither by way of the strong nor the electromagnetic force, but only through the weak force and gravity.

The Standard Model of particle physics assumes that neutrinos are massless, although adding massive neutrinos to the basic framework is not difficult. Indeed, the experimentally established phenomenon of neutrino oscillation requires neutrinos to have non-zero masses.
 
No, in this annihilation reaction you are starting out with matter in the form of an electron and a positron! The end product at low kinetic energies is 2 coincident 511 keV photons and a neutrino. This is the sort of reaction that really got people all worked up in the first place, because you have to account for the "energy loss" that is not demonstrated by the conversion of matter to energy. Hopefully, that makes sense, if not I'm sorry but I'm now fully tapped out.:(
 
kryptonite said:
So matter is produced in annihilation?
Click to expand...

Would it make more sense to say that matter was left over? The electron and positron converted to energy via the release of the 511 keV photons (gamma rays at that energy) and the neutrino, a "ghostly" particle, was the residue left over that didn't convert to energy.
 
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