Scientists in China have released details of a huge particle collider that will produce over a million Higgs bosons in a seven-year period. The conceptual design report for the China Electron Positron Collider (CEPC) calls for a 100 km underground tunnel that would smash together electrons and positrons at energies of 240 GeV. The CEPC would be a successor to the Beijing Electron Positron Collider at the Institute of High Energy Physics (IHEP), which is expected to shut down in 2020.

The CEPC, which was first proposed in 2012, is a “Higgs factory” – a facility to measure the precise properties of the Higgs boson, which was discovered at CERN in 2012 by scientists working on the Large Hadron Collider (LHC). An electron-positron machine can make much cleaner measurements than a proton collider like the LHC as its collisions do not produce as much debris. The CEPC will therefore allow the Higgs boson to be studied in unprecedented detail.

A preliminary conceptual design report for the CEPC was originally published in March 2015. That was followed by a progress report in April 2017, but the new 510-page conceptual design report, released on Sept 2 on the arXiv preprint server, outlines the technical details of the accelerator. A second volume, featuring details of the CEPC detectors, is due to be released soon.

Particle factory

Estimated to cost around $6 billion, the “heart” of the CEPC is a double-ring collider in which electron and positron beams will circulate in opposite directions in separate beam pipes. They will then collide at two “interaction points”, which will each contain a particle detector. The report reveals the CEPC will seek to generate over a million Higgs bosons over a seven-year period. The design also calls for the CEPC to operate at 91 GeV for two years to generate a trillion Z bosons as well as run at 160 GeV for a year to produce around 15 million pairs of W+ and W- particles.

Scientists will now build prototypes of key components of the accelerator and plan the manufacturing process required to construct the CEPC. If given the go-ahead by the government, construction of the CEPC could begin in 2022 and be complete by 2030. Following a decade of studying the Higgs, Z and W bosons, it is hoped that developments in magnet technology will be sufficient to begin construction of a proton-proton collider inside the existing tunnel in the early 2040s. This would operate in the range of 70-100 TeV and search for particles beyond the Standard Model of particle physics.

The location of the CEPC has not yet been decided with six locations currently satisfying the “technical requirements”. However, it is thought that the leading site is 300 km east of Beijing at the port city of Qinhuangdao. Speaking to Physics World earlier this year, IHEP director Wang Yifang says that a more detailed investigation of the geological conditions at some of the possible sites is needed before a decision can be made. “We need to know what kind of support from the local government we will receive in terms of, for example, laboratories, living conditions, roads and power supply,” he says.

Source: Physics World