[Science and Technology Frontier] The first discovery of the Full 克 Four Quick particles

【Technological frontier】

Our newspaper, Beijing, July 11th. Reporter Deng Hui learned from Tsinghua University that at the 41st International High -Energy Physics Conference in Italy recently, the compact Miaozi snail line of the European Nuclear Research Center large -scale strong collision (LHC) The tube detector (CMS) cooperation group reported that they found a strange particle family that might consist of four quackes. Professor Yi Kai of the Chinese CMS Group reported on behalf of the CMS cooperation group. The "Tsinghua-South Division" CMS group composed of researchers from Tsinghua University and Nanjing Normal University played an original and dominant role in this study.

"Because these particles are composed of the same heavy taste quark, physical images are relatively simple and easy to understand, which provides a new window for us to study strong interaction." Yi Kai introduced that this is the first time that the Chinese experimental team has observed all the full observations on LHC. ， Four Quick particles are also the first time that China has led new particles in CMS experiments.

Under the framework of particle physical standard models, the basic particles of the material world include quarks and lights. Two quarks or three quarks form the traditional meson and heavy child, collectively referred to as "traditional" strong son. In addition, the strong child, such as four or even five quarks, or those containing the ingredients of the glue, called "strange" strong son.

The theoretical scholars have predicted the existence of traditional strong and strange strong children decades ago. However, until the last 20 years, scientists have observed the more clear four quarks or five quarks. The possible peculiarizes in the early discovery include some lighter mesters, and the possibly peculiar Jiezon (3872) discovered by the Belle cooperation team in 2003 set off a wave of research on the "heavy taste" strange strong son in the world. And become one of the long -term hot spots of high -energy physics. After that, the band -charged strange son ZC (3900)+, etc. found by the Chinese BESIII cooperation group, confirmed that this kind of strange strong son is different from the peculiarity of traditional puppets -with electricity, and further pushing the research of the strange strange testers. To orgasm.

But the experimental studies of strange Johnsksuko are often full of twists and turns. For example, X (4140) particles were denied after the CDF experiment in 2009, and was denied by other experiments. It was not until 2017 that LHCB re -confirmed its existence with greater statistics, and it took 8 years to finally be recognized. Another example is the five quark state, although the beginning of this century in many experiments (the post -verification is statistical fluctuations), only the five quark state discovered by LHCB in 2015 was first widely recognized, and was selected as the world's physical physics. Top ten breakthroughs.

"I haven't found all the strange strong -son families composed of pure heavy taste quarks before, namely the peculiar particles composed of 粲 Quick or Datak." Yi Kai said.

In 2013, the CMS group of Yi Kai used the characteristics of large CMS experimental data, wide coverage rate, and good quality resolution, and used the collision data collected from 2011 to 2012. The spectrum conducted a preliminary study. In 2019, Yi Kai, a professor at the School of Physics and Technology of Nanjing Normal University, and Hu Kai, a visiting professor at Tsinghua University and Hu Zhen, an associate professor of the Department of Physics of Tsinghua University, formed a research team at Tsinghua University and Nanjing Normal University. Researchers from the two universities rely on Tsinghua University to join the CMS experiment. , Jointly formed the "Tsinghua-South Division" CMS group, and Yi Kai served as the person in charge, and Hu Zhen was the deputy person in charge. The "Tsinghua-South Division" CMS group conducted a comprehensive and systematic research on the data collected from 2016 to 2018 at low quality and light.

Based on all the "proton-proton" collision data collected from 2016 to 2018, the CMS cooperation group observed the Quanxu Squak particle family (a group of strange strong son composed of the same quack), "Tsinghua-Nan Shi" The CMS group played a dominant role in this discovery. The three resonance peaks in the family were named X (6600), X (6900), and X (7300) based on the quality, of which X (6600) and X (7300) particles were first observed in the world; 6900) The evidence of the existence of particles was observed by LHCB experiments two years ago, and the results of CMS confirmed the existence of X (6900). Yi Kai said that the discovery is an important breakthrough in the field of strange Qiangzi research: "This unique and easy -to -understand system can help the theorists to establish the final model for dozens of strange strongzes discovered in the past 20 years."

Regarding the results of the CMS experiment, Zhao Guangda, academician of the Chinese Academy of Sciences and the theoretical particle physicist of Peking University: "The discovery of the full -粲 Four Quick Family is of great significance to understand our understanding. The light Quick component, which is not very likely to form a molecular state structure formed by exchanging lights, so as to provide us with a simpler and easy -to -understand physical image. I am very happy to China experimental particle physicists It plays a dominant role in this discovery, and I hope to continue to work hard in the future work. "

Deputy Director of the National Laboratory of Brook Haiwen National Laboratory and a spokesman for D0 experiment, Dmitry Jenisov, participated in the report and discussion of the results at the meeting site.One of the most important issues, these new resonances discovered by the CMS cooperation team on the LHC pave the way to understand the interaction between basic particles more deeply, and look forward to more such exciting discoveries in the future! "CMS cooperationThe group consists of more than 4,000 members of more than 50 countries and about 240 units.Among them, members of the Chinese team are from the Chinese Academy of Sciences, Peking University, China University of Science and Technology, Beijing University of Aeronautics and Astronautics, Tsinghua University, Sun Yat -sen University, Zhejiang University, Fudan University, Nanjing Normal University and other units.In recent years, the Chinese CMS group has achieved outstanding achievements in the nature of Higgs particles and multi -boson research. The discovery of the Quansi Quark Family has further enhanced the position of the Chinese group in international cooperation.

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