The Beginnings of BES ZHENG Zhipeng IHEP 2019.9.5

Agenda Background before BEPC BEPC/BES construction Formation of BES collaboration

Background before BEPC 1956 -1965, China joined the Joint Institute for Nuclear Research (JINR) in Dubna with 10 GeV proton synchrotron . Many generations of Chinese physicists had a dream to build our own particle accelerator. After many efforts, in 1975, Chinese government approved construction of a 50 GeV proton synchrotron. Unfortunately this project was cancelled in 1980 because of the adjustment of National Economical Plan.

Most Chinese physicists strongly supported this proposal. In 1980, Prof. T.D. Lee and Prof. W. K. H.Panofsky recommended China to build a 2x2.2 GeV electron-positron collider. 1/3 of the cost of the proton accelerator Fruitful physics. Most Chinese physicists strongly supported this proposal.

At this crucial moment in 1980, in a meeting with Mr At this crucial moment in 1980, in a meeting with Mr. Deng Xiaoping, Prof. T.D. Lee elaborated : The importance to China of building a high energy physics experiment base The merits of building an electron-positron collider.

After considering Prof. T. D After considering Prof. T. D. Lee’s advice and previous advice from various aspects , Mr. Deng Xiaoping decided that the high energy physics experiment base should not be cancelled and the electron-positron collider project should be initiated .

The Beijing Electron-Positron Collider (BEPC) project was officially launched in 1983. In October 1984,Mr. Deng Xiaoping and other national leaders attended the groundbreaking ceremony of BEPC and wrote an inscription for the foundation stone.

Construction of BEPC/BES Oct.1984 —Oct.1988 Prof. Ye Minghan ，the director of IHEP, the designer of BES , formed a team with 200 more physicists and engineers for the construction of BES. All of them worked diligently to realize their dream to build a base of HEP in China.

Many difficulties we faced: Tight budget of BEPC and BES (240 million Chinese yuan, （about 70 million US dollar)) (one third for BES) Backward industry level was hard to meet the required precision of detector (MDC, Shower Counter…) Lack of experience in construction.

We took appropriate measures ,such as CPM for keeping schedule, deployment to factories for quality control…, took more efforts, worked overtime to overcome the difficulties and finally finished the construction of BEPC/BES in1988, on schedule.

叶铭汉和李政道，1983年

The first collisions of BEPC took place on October 16th, 1988.

June 22，1989, J/Ψ were found in BES. Sep. running at J/Ψ. All data showed that the detector was working well, its performance met for design requirements. In 1994, we submitted a paper “BES detector” to NIM.

The BES detector

Leaders of sub detectors and sub system Ma Jimao （MDC) Zheng Zhipeng (TOF) Zhou Yuehua( S.C), Li Jin (End cap S.C) Zhu Yonsheng(Muon C) Ni Huiling (Lum.Monitor) Zhu Shangen(Coil) Yu Zhongqiang (Trig) Zhang Changchun, Huan Yinzhi(On line) Wang Taijie, Wang Shuqing(Off line) Xi Deming(Electronics)

Formation of BES collaboration Feb - Mar 1990, Dr. Walter Toki visited IHEP. Discussed with several BES colleagues and me. Expressed that he and other American colleagues interested in BES Physics And his hope of working together.

Prior to this… Suggested American participation in the BES experiment. Prof. T. D. Lee and Prof. W. H. K. Panofsky had already approached CAS President , Prof. Zhou Guangzhao, Previous director, Prof. Ye Minghan, Suggested American participation in the BES experiment.

I agreed with the suggestion : We had already obtained a great deal of support from the US during the construction of the BEPC / BES And the joint of US physicists would be extremely helpful , especially in data analysis, where we need the expertise urgently.

In summer 1990, I met SLAC director Prof In summer 1990, I met SLAC director Prof. Burton Richter in a conference in Singapore He expressed that the physicists from SLAC and other US institutions were very interested in BES physics Asked whether it would be possible to form a China-US collaboration I gave him a positive answer and explained that CAS President Zhou Guangzhao was supportive of such idea..

In December 1990, Prof. Burton Richter visited IHEP, and finally he and IHEP director Prof. Fang Shouxian signed an MoU between IHEP and SLAC for collaboration on the BES experiment.

In February 1991, Yu Zhongqiang, Li Jin and Wang Taijie visited SLAC. In May 1991, the BES Collaboration was formally established. The first two Co-spokesmen of BES are Yu Zhongqiang and Walter Toki . Next, Li jin and Walter Toki, Joe Izen.

At that time, the Collaboration included over 70 physicists from Chinese institutions including IHEP, USTC, Shandong University, Huazhong Normal University, Peking University, Tsinghua University, Nanjing University and Nankai University……

From the US, there were over 20 participants, from 10 institutions including SLAC, Caltech, MIT, UT Dallas, Colorado State University, University of Washington at Seattle, Boston University, UC Irvine, and SSCL. Later, University of Hawaii joined as well. The collaboration slowly grew to around 150 members in total.

In August 1991, an experiment was started to measure the mass of the τ lepton. The Chinese and American participants worked together extremely well, completing this experiment and obtaining a value for the τ mass , ten times more precise than previous measurements, confirming the theory of lepton universality.

BES Collaboration Annual Meetings 1992 in Chengde. 1993 in Fragrant Hills ，Beijing, 1994 in Hangzhou. These three meetings were extremely important in improving the mechanisms of the Collaboration. Since then, the Collaboration continues to develop.

For the requirement of communication of BES Collaboration, IHEP and SLAC colleagues have done a lot of work on the internet connection and test. In 1994 IHEP built up a first internet in China.

Today, the BES Collaboration including around 500 members from 14 countries and regions – a fact that, considering the humble beginnings, I am so excited and wish BES Collaboration stronger and obtain more achievements !

Thank you for your attention!