# Electron-Positron Collision

1. Jan 20, 2010

### HarryDaniels

Edit, the title is electron, positron collision.
Sorry.

In the Feynmans Diagram involving a collision between a positron and a electron (or e+ and e-) a photon is generated and becomes a quark and anti-quark pair. Once these two are generate I know that one releases (radiates) a gluon. Can someone explain the formula and tell me whether or not this quark-antiquark pair use the gluon to become a meson?

Thank You
-Harry.

2. Jan 20, 2010

### diazona

Re: Electron-Proton Collision

In your example, for low energies, the quark and antiquark could become a meson, but at higher energies they would fly apart and combine with additional quarks/antiquarks (possibly created from ambient virtual photons, a.k.a. vacuum fluctuations) to become two distinct showers of particles, called jets. The emitted gluon can even separate from the quark and antiquark and produce a jet of its own. This is called a "three-jet event" (technical term no, really!) and it's frequently seen at large particle accelerators.

3. Jan 21, 2010

### HarryDaniels

Re: Electron-Proton Collision

Sorry,
I was thinking of another formula.

4. Jan 22, 2010

### HarryDaniels

Another Electron-positron collision

In my A-level book there is a diagram of an electron and a positron colliding and forming two EM radiation photons which go off at a 90 degree angle away from the direction in which the electron/positron hit. My problem is that in the Feynman Diagram an electron and a positron hit and one photon is created which becomes a quark anti quark pair.

Can someone explain to me why these are different?

5. Jan 23, 2010

### ansgar

first you should not think of Feynman diagrams of what is actually going on, the angles and lines etc are not REAL.

Thus the diagram in you A level book is repsenting the momentum arrows in the centre of mass frame for the electron (positron) and the photons.

Feynman diagram are something else.