View source for Circular Electron Positron Collider

{{Short description|Proposed Chinese electron–positron collider}}
The '''Circular Electron Positron Collider''' ('''CEPC''') is a proposed Chinese [[Electron–positron annihilation|electron positron collider]] for experimenting on the [[Higgs boson]]. It would be the world's largest [[particle accelerator]] with a circumference of {{convert|100|km|mi}}.<ref name="nature_2018">{{cite journal |last1=Gibney |first1=Elizabeth |title=Inside the plans for Chinese mega-collider that will dwarf the LHC |url=https://www.nature.com/articles/d41586-018-07492-w |journal=[[Nature (journal)|Nature]] |date=23 November 2018 |doi=10.1038/d41586-018-07492-w |s2cid=115440460 |access-date=26 December 2021}}</ref>

CEPC was proposed by the [[Chinese Academy of Sciences]]' [[Institute of High Energy Physics]] in 2012.<ref name="cepc_intro">{{cite web |title=The CEPC Project |url=http://cepc.ihep.ac.cn/intro.html |website=Institute of High Energy Physics |access-date=26 December 2021}}</ref><ref name="nature_2018"/> 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 {{CNY|36.4 billion}}, including experiments.<ref name="cc_2024-03">{{cite web |last1=Gao |first1=Jie |last2=Li |first2=Yuhui |last3=Yu |first3=Chenghui |title=China’s designs for a future circular collider |url=https://cerncourier.com/a/chinas-designs-for-a-future-circular-collider/ |website=CERN Courier |date=27 March 2024 |access-date=28 March 2024 }}</ref>

The design was produced by a team of international physicists.<ref name="nature_2018"/> The technical design report was released in December 2023.<ref name="cc_2024-03"/>

==Description==
CEPC is projected to have a maximum center-of-mass energy of 240 GeV.<ref name="cepc_intro"/> It will be located {{convert|100|m|ft}} underground, and have two detectors.<ref name="nature_2018"/> The electron-positron collisions will allow clearer observations than the proton-proton collisions of the [[Large Hadron Collider]] (LHC).<ref name="nature_2018"/>

After 2040, the collider could be upgraded into the Super Proton–Proton Collider<ref name="cepc_intro"/> with collision energies seven times greater than the LHC.<ref name="nature_2018"/>

==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<sup>−1</sup> with two detectors, which corresponds to approximately one million produced Higgs Bosons.<ref>{{cite web|last1=LOU|first1=Xinchou|title=Overview of the CEPC project|url=http://indico.ihep.ac.cn/event/4937/session/0/contribution/1/material/slides/1.pdf}} Workshop on Physics at the CEPC, August 10–12, 2015</ref> One target is to be able to measure the ZH production cross-section <math>\sigma(ZH)</math> 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.<ref>{{cite web|title=Probing Zbb̅ couplings at the CEPC|first1=Jiayin|last1=Gu|url=http://indico.ihep.ac.cn/event/4937/session/2/contribution/15/material/slides/0.pdf}} Workshop on Physics at the CEPC, August 10–12, 2015</ref>
* [[Physics beyond the Standard Model]]:<ref>{{cite web|title=Naturalness and Higgs Measurements|url=http://indico.ihep.ac.cn/event/4937/session/1/contribution/7/material/slides/0.pdf|last1=Craig|first1=Nathaniel}} Workshop on Physics at the CEPC, August 10–12, 2015</ref> 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

==References==
{{reflist}}

== External links ==
* Record for [https://inspirehep.net/experiments/1620741 CEPC] on [[INSPIRE-HEP]]
[[Category:Particle physics facilities]]
[[Category:Particle experiments]]
[[Category:Science and technology in China]]
[[Category:Proposed particle accelerators]]