Do we have different photon

1. May 9, 2007

guapig

when an electron meets a positron, both the electron and the positron cease to exist, and pure light comes flying out,and then the photon(light) will decay into a $$\mu^- \mu^+$$ .

MY question is what is the difference between the photon that comes from the annihilation and a normal photon which will not decay at all.

Thanks.
GUAPIG: any reply would be greatly appreciated.

Last edited: May 9, 2007
2. May 9, 2007

Sojourner01

You have things a little muddled. Electron-positron collisions produce a pair of photons, OR a pair of muons, OR - if you're lucky - a pair of tauons, or you can even get the two to transmute into one another. I believe the intermediate between all these is a virtual weak boson, but I could be misremembering.

The answer to your actual question is that there is no difference between the end products and an actual photon - because the end products ARE unambiguously real photons, or muons, or whatever.

If you're asking what the difference is between a virtual weak boson and a 'real' weak boson, there isn't as such. Virtual particles are those which are not observed but are hypothesised to exist in order to carry out interactions such as these, and as such vanish too quickly to observe.

3. May 9, 2007

guapig

Sorry,my English is bad,I could not express my idea clearly.But I really THank you Sojourner01.

maybe it is like this.When an electron-positron collision is occuring,we may get something as you said,but it is just possibility.

but I still have something unsure.I will try to work out.
THANKS AGAIN

4. May 11, 2007

ihtw

I assume you are talking about the s-channel process.

Indeed a phonton could appear in the Feymann diagram as an intermediate line, however it is a virtual photon instead of a real one. This is the case in QED.
As for weak interaction, the intermediate particle could also be a Z boson. Sometimes you will hear people talk about "on-shell" decay which means a real Z boson is created then decays. "off-shell" decay can also happen, where the Z is no longer phisical but "virtual".

Actually e+e- can not collider together can produce a single real photon. Just write the 4-momentum conservation and you can easily see that. As for a massive boson, Z in this case, such a process is possible.

However the e+e- -> 2 photon is possible through t-channel,as sojourner explained. Or check it out here
http://en.wikipedia.org/wiki/Electron-positron_annihilation