# Sillytime: Anti-matter/Matter colliders

1. Jul 11, 2012

### Quine!

So with my limited understanding of particle physics, I've gathered that the the jist of a collider is you accelerate (usually two) beams of charged particles towards each other so that they collide with the highest possible energy. The more energy you use, the more interesting your results will be, e.g. the lhc's 8 TeV collisions.

And now for an incredibly naive question:

What if you had a collider that, instead of colliding charged matter together, e.g. protons, you instead collided matter and anti-matter together. i.e. a proton beam on one track, and an anti-proton beam on the other.

I understand how this might not be technically feasible due to (1) The extremely volatility of anti-matter, what will all this matter around. and (2) The difficultly associated with producing anti-matter in any quantities whatsoever.

Lets not worry too much about (1), just keep people away from your collider, and since matter in particle accelerators is controlled using EM, you should be able to control a beam of, say, anti-protons using the same technique.

(2), however, seems like a deal breaker. I suppose if you were very efficient with your anti-protons (i.e., each anti-proton was likely to be involved in a collision), you could produce enough to do some physics.

That said, would your collisions be noticeably more energetic? If such a setup existed at the lhc, i guess both the anti-protons and protons in each beam would still only have energies of 4 TeV each? Would the explosive nature of anti-matter/matter collisions allow you to probe much smaller scales/higher energies? or would you just get a lot of photons?

2. Jul 11, 2012

### Drakkith

Staff Emeritus
3. Jul 11, 2012

### Bill_K

The Tevatron at Fermilab did exactly that, for almost 20 years.

4. Jul 11, 2012

### Quine!

great stuff!

5. Jul 12, 2012

### Staff: Mentor

In particle accelerators, every significant interaction with matter (mainly traces of hydrogen in the vacuum) causes a loss of the particle, the type does not matter.

This is a serious issue, and it limits the luminosity (and therefore the collision rate). Positrons are usually fine (and electron/positron collisons are much better than electron/electron collisions), but antiprotons are tricky. It is possible, with Tevatron as a prominent example. The LHC uses proton-proton collisions to achieve a higher collision rate.

It depends on the energy and the studied physics. At the high energy of the LHC, most interesting interactions happen via gluon-gluon collisions, and those do not care about protons/antiprotons.

6. Jul 12, 2012

### Bill_K

One advantage that matter-antimatter colliders have is that they can study asymmetric effects. For example the Tevatron reported on a measurement of forward-backward asymmetry in t-tbar production. ("Forward" in this case means the top quark heads in more or less the same direction as the proton beam.)