B How does the LHC send same charged particles against each other?

[docnet]

How does LHC send same-charged particles in opposite directions?

 

[Milsomonk]

At the LHC the counter propagating beams are transported in separate beam pipes before their paths are overlapped using magnets to cause particle collisions.

 

[Vanadium 50]

One beam has protons injected clockwise, and the other has them injected counterclockwise.

 

[ChrisVer]

I guess people already answered, but these kind of Qs can also be helped with visualization.

Here you can see the cross section of the pipe:

As also said in the comments, the bottom two pipes are where the protons travel through inside the magnets. The one is for protons moving on the clockwise and the other for the counter-clockwise direction. The top tube is for cooling down the magnets with He. We don't want collisions of protons to happen where there is nothing to look at them (although that is not always perfect).
At points where we collide protons we built the detectos such as ALICE, ATLAS and CMS. There are the points where the two beams are brought to meet each other, which would look like this sketch:
http://lhc-machine-outreach.web.cern.ch/collisions.htm

 

[mfb]

At points where we collide protons we built the detectos such as ALICE, ATLAS and CMS.

... and LHCb, to complete the list of the big detectors.

 

[ChrisVer]

... and LHCb, to complete the list of the big detectors.

well yes, maybe I should rephrase it to "we collide protons with each other". Because the LHCb is a fixed target experiment (so the beam protons are not brought together).

 

[Meir Achuz]

With the same charges, wouldn't the beams be bent in two different circles by the magnetic field?

 

[Milsomonk]

With the same charges, wouldn't the beams be bent in two different circles by the magnetic field?

They would if they were traveling through the same magnet, but they are not. As is shown in the picture handily posted by @ChrisVer, the counter propagating beams are traveling in separate beam pipes, with separate magnets.

 

[websterling]

Because the LHCb is a fixed target experiment (so the beam protons are not brought together).

Generally LHCb sees collisions of whatever the LHC is circulation (p-p, Pb-Pb, etc.) but at a lower luminosity than what ATLAS and CMS see.

Occasionally it operates in a fixed target mode where a small amount of a noble gas is injected at the collision point. This gas serves as a fixed target.

 

[vanhees71]

LHCb is not a fixed target experiment though there are ideas to use it in a fixed-target mode in the future.

 

[websterling]

See, for example-
A very special run for the LHCb experiment

The 4th paragraph describes the proton-Helium collisions as fixed-target mode.

But my main point was that LHCb does see collisions.

 

[mfb]

LHCb looks at colliding beams just like the other experiments. Yes, they have SMOG which allows looking at fixed-target collisions once in a while but that's a very rare running method.

Most B mesons produced in the symmetric collisions fly away close to the beam axis, so LHCb is built in that direction. They get ~30% of the B mesons while covering way less than 30% of the space around the collisions. Building another LHCb in the other direction would double that but would also increase the cost a lot.

 

[ChrisVer]

I agree that I was wrong here

well yes, maybe I should rephrase it to "we collide protons with each other". Because the LHCb is a fixed target experiment (so the beam protons are not brought together).

and I am sorry (especially to anyone associated with LHCb). I don't know but it was like a false idea that had gotten into my mind after a talk, and I believed it as a complete fact.