Circular Electron Positron Collider
The Circular Electron Positron Collider is an electron positron collider first proposed by the Chinese high-energy physics community in 2012. This machine could later be upgraded to a high-energy proton-proton collider, with potential far beyond the current production of the Higgs boson. The low Higgs mass of ~125 GeV makes possible a Circular Electron Positron Collider (CEPC) as a Higgs Factory, which has the advantage of higher luminosity to cost ratio and the potential to be upgraded to a proton-proton collider to reach unprecedented high energy and discover new physics. The underground particle-smashing ring aims to be at least twice the size of the globe's current leading collider - the Large Hadron Collider (CERN) outside Geneva. With a circumference of 100 kilometres (60 miles), the Chinese accelerator complex would encircle the entire island of Manhattan.
The following parameters reflect the "baseline" configuration of a collider with 53.6 km circumference and 240 GeV center-of-mass energy, and the luminosities are 3×1034, 32×1034 and 10 ×1034 cm-2s-1, respectively. The primary physics goal is to use the CEPC as a Higgs factory. Therefore, a tentative “7-2-1” operation plan is to run first as a Higgs factory for 7 years and create one million Higgs particles or more, followed by 2 years of operation as a Super Z factory to create one trillion Z bosons and then 1 year as a W factory to create about 100 million W bosons. The vast amount of bottom quarks, charm quarks and τ-leptons produced in the decays of the Z bosons also makes the CEPC an effective B-factory and τ-charm factory.  Since the project is in the early stages of planning, they are subject to change.
|Beam energy (E)||GeV||120|
|SR power/beam (P)||MW||50|
|Bending radius (ρ)||m||10,700 |
|Filling factor (κ)||0.71|
|Lorentz factor (γ)||234834.66|
|Revolution period (T0)||s||1.79·10−4|
|Revolution frequency (f0)||Hz||5591.66|
|Magnetic rigidity (Bp)||T·m||400.27|
|Momentum compaction factor (αp)||4.15·10−5|
|Energy acceptance Ring (η)||0.02|
|Cross-section for radiative Bhabha scattering (σee)||cm2||1.53·10−25|
|Lifetime due to radiative Bhabha scattering (τL)||min||56.03|
|Build-up time of polarisation (τp)||min||21|
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. One target is to be able to measure the ZH production cross-section 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.
- Physics beyond the Standard Model: 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).
- Pre-study, R&D and preparation work
- Pre-study: 2013-15
- Pre-CDR (Conceptual Design Report) by the end of 2014 for R&D funding request
- R&D: 2016-2020
- Engineering Design: 2015-2020
- Construction: 2021-2029
- Data taking and experiments: 2030-2040
- Installation of superconducting magnets upgrades for the SPPC project: 2040 and beyond. 
Possible Construction Locations
CEPC is conducting country wide site visits and study. Local government agencies are very receptive and supportive to CEPC. CDR study is based on site 1 (Qing Huang Dao). The site selection is still in processing, and CEPC team keep looking for more site candidates in China. Below are a list of possible locations:
- Qinhuangdao, Hebei Province.
- Huangling, Shanxi Province.
- Shenshan, Guangdong Province.
- Baoding, Hebei Province.
- Huzhou, Zhejiang Province.
- Chuangchun, Jilin Province.
- Changsha, Hunan Province.
- http://cepc.ihep.ac.cn/ Circular Electron Positron Collider - CEPC
- http://www.aljazeera.com/indepth/features/2014/09/china-unveils-world-largest-supercollider-science-physi-2014919131524321817.html China plans world's largest supercollider
- http://cepc.ihep.ac.cn/intro.html The CEPC Project
- LOU, Xinchou. "Overview of the CEPC project" (PDF). Workshop on Physics at the CEPC, August 10–12, 2015
- Gu, Jiayin. "Probing Zbb̅ couplings at the CEPC" (PDF). Workshop on Physics at the CEPC, August 10–12, 2015
- Craig, Nathaniel. "Naturalness and Higgs Measurements" (PDF). Workshop on Physics at the CEPC, August 10–12, 2015