Note that the China Daily article above incorrectly suggests that they will build a 50-70km circular electron-positron accelerator at ~100 TeV CoM. In fact, the project comes in two phases inside the same tunnel: first a 250 GeV electron-positron ‘precision’ machineNote that the 250 GeV electron-positron collisions will produce only one Higgs, and the fact that the COM energy is double the Higgs mass is a coincidence. See slides 9-16 here for some of the processes that will be studied.a , the Circular Electron-Positron Collider (CEPC), followed by an upgrade to a 70 TeV proton-proton ‘discovery’ machine, the Super Proton-Proton Collider (SPPC). The current timeline for operations, which will inevitably be pushed back, projects that data taking will start in 2028 and 2042, respectively. (H/t Graeme Smith.)
The existence of this accelerator has lots of interesting implications for accelerators in the Wester hemisphere. For instance, the International Linear Collider (ILC) was planning on using a ‘push-pull’ configuration where they would alternate beam time between two devices (by keeping them on huge rolling platforms!). The idea is that having two completely separate and competing detectors is critical for maintaining objectivity in world where you only have a single accelerator. Since ILC is linear, there is only one interaction region (unlike for the common circular accelerator). So to use two detectors, you need to be able to swap them in and out! But this becomes largely unnecessary if CEPC exists to keep ILC honest.
I think this is a bad development for physics because I am pessimistic about particle accelerators telling us something truly deep and novel about the universe, at least in the next century.… [continue reading]