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 80 kilometres (49.70 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 2×120 GeV center-of-mass energy. Since the project is in the early stages of planning, they are subject to change.
|Beam energy (E)||GeV||120||Lorentz factor (γ)||234834.66|
|Circumference (C)||km||53.6||Revolution period (T0)||s||1.79·10−4|
|Luminosity (L)||cm−2s−1||1.80·1034||Revolution frequency (f0)||Hz||5591.66|
|SR power/beam (P)||MW||50||Magnetic rigidity (Bp)||T·m||400.27|
|Bending radius (ρ)||m||6094||Momentum compaction factor (αp)||4.15·10−5|
|NIP||2||Energy acceptance Ring (η)||0.02|
|nB||50||Cross-section for radiative Bhabha scattering (σee)||cm2||1.53·10−25|
|Filling factor (κ)||0.71||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: 2021-2027
- Data taking: 2028-2035
- 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