Circular Electron Positron Collider Explained

The Circular Electron Positron Collider (CEPC) is a proposed Chinese electron positron collider for experimenting on the Higgs boson. It would be the world's largest particle accelerator with a circumference of 100km (100miles).^[1]

CEPC was proposed by the Chinese Academy of Sciences' Institute of High Energy Physics in 2012.^{[2] [1]} Projections in 2023 were for a proposal to be submitted to the government in 2025, and construction taking place from 2027 to 2035; the projected cost was, including experiments.^[3]

The design was produced by a team of international physicists.^[1] The technical design report was released in December 2023.^[3]

Description

CEPC is projected to have a maximum center-of-mass energy of 240 GeV.^[2] It will be located 100m (300feet) underground, and have two detectors.^[1] The electron-positron collisions will allow clearer observations than the proton-proton collisions of the Large Hadron Collider (LHC).^[1]

After 2040, the collider could be upgraded into the Super Proton-Proton Collider^[2] with collision energies seven times greater than the LHC.^[1]

Physics program

The CEPC enables a wide physics program. As an electron-positron collider, it is suited to precision measurements, but also has strong discovery potential for new physics. Some possible physics goals include:

• Higgs measurements: Running slightly above the production threshold for ZH, the CEPC is a Higgs factory. Over the course of a ten-year run, it is planned to collect 5 ab⁻¹ with two detectors, which corresponds to approximately one million produced Higgs Bosons.^[4] One target is to be able to measure the ZH production cross-section

\sigma(ZH) to 0.5% accuracy. Other goals include the measurement of the Higgs Boson self coupling, and its coupling to other particles.

• When running at the Z peak, a precision measurement of the Z Boson mass and other properties, e.g. the Zbb̅ coupling, can be made.^[5]
• Physics beyond the Standard Model:^[6] Despite the lower center-of-mass energy compared to the LHC, the CEPC will be able to make discoveries or exclusions in certain scenarios where the LHC cannot. A prominent situation is when there is supersymmetry, but the masses of the superpartners are very close to each other (near-degenerate). In this case, when one SUSY particle decays into another plus a Standard Model particle, the SM particle will likely escape detection in a Hadron collider. In an e+e- collider, since the initial state is completely known, it is possible to detect such events by their missing energy (the energy carried away by SUSY particles and neutrinos).

See also

• Large Electron–Positron Collider - LEP was the highest energy lepton collider ever built
• Compact Linear Collider – another post-LHC linear particle accelerator planned at CERN
• International Linear Collider – another post-LHC linear particle accelerator planned in Japan
• Future Circular Collider – a proposed 100 TeV circular collider at CERN

External links

• Record for CEPC on INSPIRE-HEP

Notes and References

1. Gibney . Elizabeth . Inside the plans for Chinese mega-collider that will dwarf the LHC . . 23 November 2018 . 10.1038/d41586-018-07492-w . 115440460 . 26 December 2021.
2. Web site: The CEPC Project . Institute of High Energy Physics . 26 December 2021.
3. Web site: Gao . Jie . Li . Yuhui . Yu . Chenghui . China’s designs for a future circular collider . CERN Courier . 27 March 2024 . 28 March 2024 .
4. Web site: LOU. Xinchou. Overview of the CEPC project. Workshop on Physics at the CEPC, August 10–12, 2015
5. Web site: Probing Zbb̅ couplings at the CEPC. Jiayin. Gu. Workshop on Physics at the CEPC, August 10–12, 2015
6. Web site: Naturalness and Higgs Measurements. Craig. Nathaniel. Workshop on Physics at the CEPC, August 10–12, 2015