Why electrons and positrons? Why specifically this?

Electrons and positrons, when they collide, the environment is incredibly clean.

The advantage of protons and protons is you can go to very high energies without suffering this problem of synchrotron radiation I said earlier.

But environment is very messy.

There are backgrounds.

So if you're wishing to study the Higgs boson, for example, you can only really spot the appearance of the Higgs boson in a collision if it does something very dramatic, very unusual.

From this, the LHC has made some very important measurements.

It hasn't been met with universal acclaim in the physics community, has it? There's been some physicists who are quite critical of the proposal and the scale and say that the money could be better spent on smaller projects and more smaller projects.