Large Hadron Collider - Few Questions

[Zak.azeemi]

Can anyone explain a bit how does the LHC uses magnetic filed to accelerate protons?
And why does it use protons for the collision?
Couldn't they have used electrons?

 

[lpetrich]

The LHC, like many other particle accelerators, accelerates particles using microwaves. Their electric fields kick the particles forward as they pass.

The LHC's magnets, like those of other circular particle accelerators, are for keeping the particles confined in it, not for accelerating them.

The LHC uses protons and not electrons, because electrons would radiate too much synchrotron radiation, a side effect of being continually deflected. That's because electrons are nearly 2000 times less massive than protons, and thus approach much closer to c for the same energy, giving them a 2000-times-higher gamma factor.

 

[Drakkith]

As the post above says, electrons would radiate away too much of their energy. The smaller the mass, the more energy a particle will radiate away as it is accelerated or decelerated away from its path. Also, protons fit better for the experiments they are running.

 

[lpetrich]

It must be pointed out that electron-positron collisions are much "cleaner" than proton-proton or proton-antiproton ones. That's because they are not strongly-interacting composite systems, as (anti)protons are.

When an electron and positron meet each other, they will produce a virtual photon, and with enough energy, also a virtual Z. They may also produce a virtual Higgs, but because of the electron's low mass, that particle will have a VERY small amplitude.

In fact, there's an International Linear Collider being planned, and an important question of its design is how much energy it should accelerate its electrons and positrons to. It should be enough to make interesting new particles, but it should not be enough to make the accelerator too difficult to finance.

That's where the LHC will come in. It should be able to make at least some of the particles that the ILC is to produce, and knowing their energies will help the ILC's designers work out what to shoot for.