[avz]

The paper describes a design for a linear accelerator that would reach 250GeV in center of mass frame and that may be extended to 550GeV (see section 2) and even multi-TeV (see section 5).

I was curious how this compares against LHC which Wikipedia [1] says reached record 13TeV total collision energy. However, it isn't clear whether Wikipedia cites energy in center of mass frame that could be directly compared.

Does anyone know how the two accelerators would compare in this respect? In particular, would the proposed C³ accelerator actually achieve higher total collision energy than LHC or is it instead hoped that future extensions of a C³ accelerator would exceed LHC's capabilities?

[1]: https://en.wikipedia.org/wiki/Large_Hadron_Collider

[prof-dr-ir]

Good question, and the answer is not easy.

It looks like the proposed accelerator smashes electrons and positrons together which are nice and clean elementary particles (as far as we know), so much of the collision energy is directly usable to create, say, Higgs bosons with a mass of 125GeV.

At the LHC they smash protons into each other which at this scale are a bit like a soupy mess of quarks and gluons. So its 13 TeV c.o.m. energy actually gets spread out over multiple elementary particles, which might not even hit each other straight on. Because of this the number of high-energy collisions between elementary particles is significantly lower.

This is just my lay-physicist perspective by the way; an accelerator specialist can probably provide more details.

[tobias2014]

The difference is that the LHC is a proton-proton collider, and the proton constituents (partons) that participate in the "hard" collision only have a fraction of the total energy, given by some probability distribution (parton distribution functions). For an e+e- machine you essentially use the full energy in the hard collision.

[quantum_mcts]

https://physics.stackexchange.com/q/53558/386