[Jizzle]

I'm under the impression that the reason we couldn't confirm the Higgs boson before the LHC was that electron-positron colliders could not easily produce the massive particles needed. Proton-proton or Proton-antiproton collisions seem to be much more useful for Higgs production. The Large Electron–Positron Collider almost got us there and it exceeded 200 GeV. What then would a 250 GeV machine do for us?

[mattheww]

The argument in favor of an electron-positron collider is that there is much less "junk" in the detector from the hadron collision. So the trade-off is that you produce a lot fewer Higgs bosons, but, in principle, you are able to measure each Higgs much more precisely. Having a machine at 250 GeV puts us at the sweet spot for producing the Higgs with mass 125 GeV.

There is some discussion in the community about whether it truly is going to advance the field to build such a machine. It's not super clear whether the various proposed 250 GeV machines will improve on what will be done by HL-LHC. From the Chinese point of view, though, it absolutely is the right decision to build this machine on the way to a 100 TeV hadron collider, since they desperately need to build up some local expertise in constructing/operating a large collider.

[Jizzle]

Ah, thanks. This gives me better perspective.