Antimatter

[Ashish]

Mod note: posts moved/copied from vacuum thread

 

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That was something I was wondering, I assume that you can get photon-antiphoton pairs created...

Please tell me about antiphotons or it is just lik ean antiparticle of it.

[Klaynos]

Yes but not on only one electron but it takes huge numbers of electron to come upto results of old ones.

But I think that from this (double-slit experiment with photons or other microscopic particles) that there is nothing like waves.

 

You do need many particles to form the interferance pattern, but if you fire them one at a time you get the same result as if you use a continuouse stream of them (it just takes more time) this means that the individual particle has traveled through both slits. This experiment has been preformed with things as large as buckminster fullerenes...

 

Please tell me about antiphotons or it is just lik ean antiparticle of it.

 

Yes, but it is indistinguishable from a normal photon.

[5614]

Yes, but it is indistinguishable from a normal photon.

A photon is it's own antiparticle. That is, the photon and anti-equivalent of it are in fact the same thing, you cannot distinguish between them. Physically speaking an antiphoton does not exist.

 

One way of mathematically defining antimatter is that it is what would occur if matter went back in time. An electron travelling backwards in time is mathematically identical to a positron travelling forward in time. I suppose if you were to try and extend this to a photon I might argue that a photon does not experience time, and thus saying it is going backwards through time is non-sensical.

 

Any massless gauge bosons (force carriers) does not have an antiparticle. I think that photons, W & Z bosons and gluons are the only particles without an antiparticle.

 

At an educated guess I would extend this to say that any massless particle will travel at c and will not have an antipaticle. True?

 

This all also ties in nicely with Feynman diagrams. In FDs you don't need to refer to antipaticles, you can just label, for example, all positrons as electrons going backwards through time. Of course often positrons will be named, for simplicity. Also the whole no antiparticle thing would explain why photons (and other force carriers) are often drawn without arrows on them. Although there seems to be a lot of different ways of doing FDs, some do not have a time axis, in those this paragraph is not necessarily relevant.

[thedarkshade]

One way of mathematically defining antimatter is that it is what would occur if matter went back in time. An electron travelling backwards in time is mathematically identical to a positron travelling forward in time. I suppose if you were to try and extend this to a photon I might argue that a photon does not experience time, and thus saying it is going backwards through time is non-sensical.

One thing I learned at school is to cut details when possible, and I think that applies here too! What you have said is a brilliant interpretations but I think it should be less complicated than that.

 

I was thinking like, antimatter is the same as ordinary matter but only with opposite charge. Electron vs. positron & proton vs antiproton both result in annihilation and complete release of energy. And a photon does not have charge, hence it cannot have antimatter! The oposite of zero is still zero!

[swansont]

One thing I learned at school is to cut details when possible, and I think that applies here too! What you have said is a brilliant interpretations but I think it should be less complicated than that.

 

I was thinking like, antimatter is the same as ordinary matter but only with opposite charge. Electron vs. positron & proton vs antiproton both result in annihilation and complete release of energy. And a photon does not have charge, hence it cannot have antimatter! The oposite of zero is still zero!

 

Antineutron

Antineutrino

[thedarkshade]

Is that an annihilation process? Because neutrons have no charge, so you can't really cancel charges when you have no charge at all, and I find that a bit strange. Or is it just a fancy way of doubting a post?

[Klaynos]

Is that an annihilation process? Because neutrons have no charge, so you can't really cancel charges when you have no charge at all, and I find that a bit strange. Or is it just a fancy way of doubting a post?

 

The two particles he mentioned both have no charge, but are anti particles that will annihilate when they encounter their normal pair.

 

So:

 

neutrino - antineutrion

neutron - antineutron

[iNow]

Hence, the comment you made above (quoted below) is just wrong.

 

antimatter is the same as ordinary matter but only with opposite charge.

 

 

Sometimes, removing details and simplifying things makes matters WORSE!

[ydoaPs]

Is that an annihilation process? Because neutrons have no charge, so you can't really cancel charges when you have no charge at all, and I find that a bit strange. Or is it just a fancy way of doubting a post?

It's not just charge. Anitparticle have other qualities(like spin) that are opposite of their matter counterparts.

[swansont]

It's charge + parity (CP), which is why (AFAIK) that antiparticles look like regular particles moving back in time. Because if you reverse CP, and also T, then CPT symmetry still holds — everything looks normal.

 

(of course, CP is violated on rare occasion, with reactions giving more matter than antimatter)

[Royston]

Any massless gauge bosons (force carriers) does not have an antiparticle. I think that photons, W & Z bosons and gluons are the only particles without an antiparticle.

 

Just to clarify, (I'm sure 5614 knows this) but W & Z bosons are not massless, approximately 80 Gev/c2 and 91 GeV/c2 respectively. Unlike the photon (and graviton if it exists) which are massless, and giving EM and gravity fields infinite range, the bosons range is limited due to their large mass. The gluon, although massless doesn't have an inverse square equation describing it's force.

 

IIRC there are two types of W boson, which both have charge W+ W-, and one is the antiparticle of the other, the Z boson has no charge and so it's antiparticle is the Z boson, similar to the photon's antiparticle being the photon (they're their own antiparticle.)

[5614]

thedarkshade: if you consider a proton as a confined system of 3 quarks then maybe it's more (for want of a better word) obvious that it can have an antiparticle. The antiproton is made of 3 antiquarks. But alas, neutrinos have antineutrinos, so this way of thinking cannot be extended to everything.

 

 

Snail: actually, that last post of mine is a bit wrong (shame I can't now edit it). Photons, Z bosons & gluons are their own antiparticles. But you are correct; W+/W- are a particle/antiparticle pair.

 

So a W+ and a W- boson should annihilate each other but does anyone know an example of when/how this might occur? In what practical scenario would a W+/- be in such close proximity?

[timo]

So a W+ and a W- boson should annihilate each other but does anyone know an example of when/how this might occur? In what practical scenario would a W+/- be in such close proximity?

Vector boson fusion, a possible channel for Higgs discovery.

(image from Wikipedia Commons)

 

Not sure if intermediate W's are what you call "W's in close proximity", but you won't find many of those unstable particles flying around freely.

[thedarkshade]

thedarkshade: if you consider a proton as a confined system of 3 quarks then maybe it's more (for want of a better word) obvious that it can have an antiparticle. The antiproton is made of 3 antiquarks.

That is out of consideration! Quarks have rest mass. Photons don't! It is a very rough attempt to clarify!

 

What wasn't clear for me is that I thought annihilation process took place only by opposite charge!