BEIJING—An éminence grise in particle physics, Nobel laureate Chen Ning Yang, has come out strongly against plans to build the world’s largest particle accelerator in China. His comments come at a critical time for the Circular Electron Positron Collider (CEPC), one contender to succeed the Large Hadron Collider (LHC) in Geneva, Switzerland. Debate is now intensifying over whether the CEPC’s science questions are compelling enough to justify the estimated $6 billion price tag, 70% of which China would bear with as-yet unidentified partners covering the rest.
Leading the charge for the CEPC is the Chinese Academy of Sciences’ (CAS’s) Institute of High Energy Physics (IHEP) here. For 30 years, the institute has operated the Beijing Electron Position Collider (BECP), a small machine that put China on the map in high-energy physics. With the BECP set to shut down in 2022, researchers here for the past decade have been mulling a successor. In September 2012, 2 months after the LHC announced the discovery of the Higgs particle, IHEP proposed the CEPC and an even more ambitious upgrade down the road. However, its request for about $120 million over 5 years for conceptual design work on the CEPC failed to win approval earlier this year from China’s National Development and Reform Commission; instead, the project received some $5 million for preliminary study.
On 4 September, Yang, in an article posted on the social media platform WeChat, says that China should not build a supercollider now. He is concerned about the huge cost and says the money would be better spent on pressing societal needs. In addition, he does not believe the science justifies the cost: The LHC confirmed the existence of the Higgs boson, he notes, but it has not discovered new particles or inconsistencies in the standard model of particle physics. The prospect of an even bigger collider succeeding where the LHC has failed is “a guess on top of a guess,” he writes. Yang argues that high-energy physicists should eschew big accelerator projects for now and start blazing trails in new experimental and theoretical approaches.
That same day, IHEP’s director, Wang Yifang, posted a point-by-point rebuttal on the institute’s public WeChat account. He criticized Yang for rehashing arguments he had made in the 1970s against building the BECP. “Thanks to comrade [Deng] Xiaoping,” who didn’t follow Yang’s advice, Wang wrote, “IHEP and the BEPC … have achieved so much today.” Wang also noted that the main task of the CEPC would not be to find new particles, but to carry out detailed studies of the Higgs boson.
Yang did not respond to request for comment. But some scientists contend that the thrust of his criticisms are against the CEPC’s anticipated upgrade, the Super Proton-Proton Collider (SPPC). “Yang’s objections are directed mostly at the SPPC,” says Li Miao, a cosmologist at Sun Yat-sen University, Guangzhou, in China, who says he is leaning toward supporting the CEPC. That’s because the cost Yang cites—$20 billion—is the estimated price tag of both the CEPC and the SPPC, Li says, and it is the SPPC that would endeavor to make discoveries beyond the standard model.
Still, opposition to the supercollider project is mounting outside the high-energy physics community. Cao Zexian, a researcher at CAS’s Institute of Physics here, contends that Chinese high-energy physicists lack the ability to steer or lead research in the field. China also lacks the industrial capacity for making advanced scientific instruments, he says, which means a supercollider would depend on foreign firms for critical components. Luo Huiqian, another researcher at the Institute of Physics, says that most big science projects in China have suffered from arbitrary cost cutting; as a result, the finished product is often a far cry from what was proposed. He doubts that the proposed CEPC would be built to specifications.
The state news agency Xinhua has lauded the debate as “progress in Chinese science” that will make big science decision-making “more transparent.” Some, however, see a call for transparency as a bad omen for the CEPC. “It means the collider may not receive the go-ahead in the near future,” asserts Institute of Physics researcher Wu Baojun. Wang acknowledged that possibility in a 7 September interview with Caijing magazine: “opposing voices naturally have an impact on future approval of the project,” he said.