The mystery of exploring quality origin: Higgs particles discovery process and future Higgs factory (below)

05

High -energy collision machine: weapon for particle physics research

Standard models have become the basic assumptions that can describe the interaction of basic micro -particles and the electromagnetic, strong nuclear force, and weak nuclear force between them. However, no matter how beautiful the theory is, an unprecedented standard model is still just an empty building. Only the theory verified by the experiment is the truth. At this time, although the blueprint of the standard model is in hand, if you want to draw it according to the picture, prove that it needs tools. If you want to be good, you must first benefit your instrument. If you want to find these particles, the most tool for particle physicists is the high -energy collision.

The collision machine is a class of scientists used by scientists studying particle physics. It is a super microscope that can deepen human cognition to a micro -world less than an atomic scale. The collision opportunities accelerate the micro -particles such as electron, protons, or heavy ions, so that they can run in the pipeline at a speed of light, and then the two beams of particles are focused and collided at extremely high energy in the detector. Two particles that come together have gone through extremely complex physical processes at the moment of the collision, generating a large number of new particles with high energy. These new particles are then sprayed around the space around and received by the detector around the collision point. Physicists can analyze the physical processes of collisions by studying the collision product detected by the detector. Due to the small objects studied by particle physics and the energy required so high, scientists can only obtain high energy required by the research by building large -scale accelerated instruments.

In the 1960s and 1970s, scientists built more than a dozen colliders in some powerful universities or research institutes in France, the United States, the Soviet Union, Germany and other countries. The size of these collisions is huge, from a few meters to a week length of two kilometers, covering many different energy intervals, and can study different specific topics separately. At that time, as scientists began to master the research weapon of collisions, particle physics showed a round of explosive development. As mentioned earlier, Kakka, as well as the bottom quark and top quark, W ± and Z0 boson are found through the collision experiments. With the deepening and progress of research, the subject of low energy interval can no longer meet the needs of theoretical development. Scientists have begun to need to be more and more energy collision to carry out scientific research. The medium and small collision machines gradually leave the focus that scientists care about. Only some collisions running in a specific energy range have been retained for some special needs. The larger the construction machine, the higher the cost of the collision machine, the higher the construction of a large collision machine. In this process of continuous development, particles physicists working in different institutions have gradually begun to unite and have launched global cooperation.

In the late 1970s, physicists at the European Nuclear Research Center began to consider the strategy of long -term physics development. The plan to build a "large -scale electronic collision" (LEP) with a length of 27 kilometers began to surface. After several years of design and demonstration, on May 22, 1981, the European Nuclear Research Center finally approved the grand project. After the construction and installation from 1983 to 1988, the large positive and negative electronic collision LEP was officially launched in 1989. The perimeter of 27 kilometers has also made it the largest scientific research instrument in human history to date.

However, the LEP launched in Europe in 1989 was not the highest energy collision that year, because since 1986, the highest crown of collision energy has always been hung on a collision head in the United States. At the end of 1986, in the Fermi National Laboratory in the United States, a 6.3 -kilometer positive and anti -proton collision machine "TEVATRON" officially began to run with unprecedented collision energy, and Tevatron created 1.96 TEV's energy records have been maintained for more than 20 years, and it was not broken by the large strong child collision (LHC) of the European Nuclear Research Center until 2010.

Why was the larger and updated collision LEP below Tevatron? This is because, although it is also called a collision machine, LEP and Tevatron belong to two different types of scientific research instruments. They are positive and negative electron collision machines and strong collisions. As their names described, the collision particles in the positive and negative electronic collision were positive electrons, and the particles that collided in the strong collision can be proton or heavy ions. Electronics is an indispensable basic particle. This particle is charged, and the volume is considered to be approaching zero. The physical process that electronics can participate in the collision is very simple, the collision product is very clean, and it is very suitable for experiments that are used for accurate measurement. The same stable production products. However, electronics has a very helpless feature that the experimental physicist is very helpless, that is, the electrons will radiate a lot of energy when turning, thereby reducing the energy that comes with the electrons itself. In addition, the more severe the electronic turning, the greater the radiation energy. Therefore, the electronic collision machine usually makes a large radius ring, or accelerates electrons directly in a straight line. The "Stanford Straight Accelerator collision" (SLAC) located in the United States is an experimental instrument that accelerates electrons to accelerate in a straight line. The disadvantage of the linear accelerator is that the electron beam cannot be reused. After the collision is once, all the accelerated electrons will be wasted, and the ring -type collision machine can make the accelerated particles repeatedly used again and again, thereby saving saving Particles and energy. Positive electronic collision machines do not need a strong magnetic field to restrict the particles because their radius and low energy, so the manufacturing process is relatively simple. The most common particles in the collision in a strong collision are proton, which is the atomic nucleus of the hydrogen. Proton is not basic particles in particle physics. The proton contains three quarks and some gels that connect the quarks. Quicks and gum will participate in complex physical processes during collisions. The collision products will be very complicated and diverse. They cannot have a stable output as positive and negative electron collision particles factories. However, because the quality of proton is much greater than electronics, only less energy is radiated when turning, so protons can get much higher energy than electrons in the accelerator. Johnson collision machine is suitable for "opening Xinjiang to expand" and use extremely high energy to explore the problem of frontier energy. Research physical problems with a strong collision machine is a process of "strong miracle". The extremely high energy means that the tough collision must use a high -intensity magnetic field, so a large amount of superconducting materials are required. Hideko collision is not good at doing very precise measurement, but it is suitable for exploring new physical phenomena.

The LEP and Tevatron in the previous article have played a huge role in the verification process of the standard model. One of their physical goals contains the search for Higgs particles. Especially around the new century, the basic particles in the standard model include Quark, all of which have been discovered, and only Higgs particles have not been discovered. However, after many years of operation, although LEP and Tevatron have achieved remarkable results in other fields, they have been sinking on the road of the Higgs particles. Although more and more people have believed in standard models, the absence of the Higgs particles has made the standard model still the air pavilion.

In the 1980s, the U.S. superconducting super collision machine (SSC), which was pre -research almost at the same time as LHC, was much larger than LHC. In 1982, American scientists put forward the idea of ​​building SSC. Its ring tunnel was 87 kilometers long, and the energy of proton collision was 40 TEV, which was three times that of the LHC design energy. In 1983, the US Department of Energy approved SSC's pre -research, and the SSC project was officially launched in January 1987. In November 1988, it was determined to be located in Texas. Construction began in 1991. At this time, a redesigned SSC project valuation rose from 4.4 billion to $ 8.25 billion. It is expected to be put into operation in 1999. However, only two years later, the National Audit Agency's audit believe that SSC project costs were overdue and progress was lagging. As a result, the SSC, which has a lot of life journey, experienced the design plan after the construction of the coach before the construction of the construction. The new plan has greatly increased the budget, the different opinions of the academic community, and the Republican president who supported the collision in the rotation of the party, the end of the Cold War, and the United States and the Soviet Universes. Under the combination of various internal and external pressures, it was finally officially announced on October 21, 1993 by the US Congress.

According to the design of SSC, its ability should be so powerful, so that today, more than thirty years later, there are still no collisions in the world. If it does not experience those twists and turns, it is almost the best hunter in Higgs particles. However, history must not be assumed. Because of the suspension of SSC, the United States has lost its long -term hegemon position in the field of high -energy physics.

06

Large -scale strong collision machine: the discovery of Higgs Bolometer

In the 1980s, who could have thought that in the attitude towards science, a quarter of Europe was more united than unified United States. As early as 1984, the LEP of the European Nuclear Center officially started five years before, when LEP was still under construction, European scientists considers the future of LEP after retirement. At a discussion in 1984, scientists proposed the first proposal to build a new "large strong collision" LHC in the tunnel that use the LEP retired tunnel. However, this proposal has not formed a complete proposal for a long time and was approved. The reason is that at this time, the LEP is still in the construction stage, and it is too early to retire from it. Approval. The existence of SSC has made European plans lose its competitive advantage, and whether LHC is necessary to be built and draw on a question mark. However, after SSC was suspended in 1993, it lost the competition of the American SSC. European LHC became the only collision scheme in the world that was expected to solve major particle physics such as Higgs particles. Therefore, in 1994, the LHC construction plan was officially approved by the European Nuclear Research Center. In 2000, LEP officially ended its data acquisition process for more than ten years, and was completely demolished in 2001. The 27 -kilometer tunnel left by LEP was reorganized for LHC. In addition to a 27 kilometer -long tunnel occupied by LHC, there are several accelerator rings that are accelerated step by step. The complex and huge structure makes it refresh the record of the largest scientific research instrument built in human history. For a behemoth with a sci -fi color, the surface range of the space occupied by the accelerator ring is refers to Figure 5. The LHC is not only large, but also the design collision energy has also reached an amazing 14 trillion electron volt, which is equivalent to accelerating each proton at a voltage of 7 trillion volts, far exceeding its predecessor LEP and American competitors Tevatron Essence The energy obtained by the proton in the accelerator can reach nearly 10,000 times its own quality. In the 27 kilometer accelerator ring, the frequency of 11,000 times per second, the speed reaches 99.99%of the speed of light, and can occur up to 1 billion times per second. Campaign case. The fierce collision of protons can simulate the high temperature and high energy state of the Big Bang of the Universe. The instantaneous temperature generated by the collision can be compared with the state of the cosmic bang (about 10 ~ 12s). Persia physicists use the product of proton collision to detect new particles and new physical phenomena, for example, to find the Higgs particles with standard model predictions, and explore new physics beyond standard models such as super -specific, additional dimensions, and dark matter.

Figure 5 The European Nuclear Research Center Large Strong Child collision machine overlooks the picture

LHC mainly conducts four large -scale experiments, including ATLAS (ultra -ring instrument experiments), CMS (compact Miaozi coil experiment), Alice The well -deserved model. Among them, ATLAS and CMS are two multi -purpose large -scale detectors, which are used to analyze the huge number of particles generated during the collision of the accelerator -proton -proton collision. The scale of the two experiments has reached unprecedented levels. See Figure 6 during the construction process. The ATLAS detector is 46 meters long, 25 meters wide, 25 meters high, and the total weight is about 7,000 tons. It has nearly 100 million electronics reading channels. It is by far the largest particle detector in the world. The CMS detector is 21 meters long, 15 meters wide, 15 meters high, and weighs about 12500 tons. ATLAS and CMS detectors are equivalent to a giant digital camera and microscope. They can shoot 4 million times per second to record the particles information generated by hundreds of millions of collision cases between protons for analysis. The two large international cooperation experiments groups of ATLAS and CMS each have about 5,000 researchers and engineering technicians, and more than 300 research institutions from more than 60 countries and regions.

Figure 6 ATLAS (above) and CMS (below) detector

However, LHC is a difficult machine that is difficult to be tamed, and its start -up phase is full of twists and turns. In 2008, during the trial operation phase of LHC, the high -current high current through a section of the welded connection line penetrated the liquid storage tank of the cooling equipment. As high as 6 tons of liquid leakage into the tunnel, the leakage volume reached about 1/3 of the total amount of liquid pupa. This makes LHC have to take a year for maintenance and review. However, regardless of the external expectations of LHC or joy or sadness, after experiencing a difficult start -up stage, LHC officially started operation and obtaining collision physical data in 2010, and it also easily won the creation of humans on the earth on the earth. Records of the highest energy. And two years later, in 2012, it successfully discovered Higgs Bose.

On July 4, 2012, it is destined to be an unusual day. The European Nuclear Research Center CERN held a global press conference, announcing that the two large experimental groups of ATLAS and CMS of LHC also found new particles with a mass of about 125 GEV, signals, and signals. The intensity reaches and exceeds the five standard deviations of the confidence of the new discovery of the particle physicist, that is, the possibility of error judgment is less than one -3 millionth. The characteristics of new particles are similar to the "Higgs Boller", which has been working hard in the physics community of particles, and is called "God particles". See Figure 7. This is the result of the hard work of thousands of scientists around the world for half a century. Both the world's all thousands of media and radio reports this epoch -making great discovery, for example: the New York Times reported that "scientists have discovered mysterious particles that are vital to the universe"; "Sri Lanka"; The British Guardian titled "The discovery of the Higgs particles was another huge leap of human beings. This great achievement is comparable to humans to the moon and is worthy of everyone's pride." CERN's director of the chief Director of the CERN claimed: "Human beings have crossed into a new stage in understanding the nature of nature." Figure 7 large -scale strong child collision experiment found that Higgs particles were found

At this time, the Standard Model Building is no longer the air pavilion, and all the basic particles it predicted have been discovered. At this moment, the proposal of the Higgs mechanism has passed 48 years. The discovery of Higgs Boson fills the standard model and is the most important cornerstone. In a sense, the standard model is completed, becoming a major milestone in particle physics research.

07

Future Road: Higgs Factory

The discovery of Higgs particles in 2012 was regarded as a major breakthrough in human understanding of the universe since the atomic structure revealed, and this breakthrough has opened a new era of particle physics. On the one hand, although the framework of the standard model has been completed, the details are still unclear, and there are a large number of uncertain conditions, so all theories based on the Higgs mechanism and standard model can be boldly advanced and proposed more detailed. Experimental requirements. On the other hand, physicists are also very clear that the current standard model is incomplete. There are many experimental observation results conflicting with the predictive prediction of the standard model. For example, in the standard model framework The experimental results of micro -oscillations show that neutron is quality. The standard model cannot describe dark matter, so the theory of new physics beyond the standard model still has a lot of possibilities. The Higgs particles are not only related to the origin of the quality of basic particles. Other major cutting -edge scientific issues such as the process of early cosmic evolution, dark matter and dark energy are also closely related to the Higgs particles. See Figure 8. Therefore, the precise study of Higgs particles is an important physical goal that needs to be completed in a very clear future in the particle physics community.

Figure 8 The relationship between Higgs Physics and other scientific issues

After years of in -depth discussions in the international high -energy physics community, consensus has gradually formed, that is, hoping to use positive and negative electron colliders to produce a large number of Higgs particles (that is, the "Higgs Factory"). Mainly because in the LHC experiment of a large -scale strong child collision, a lot of strong sub -bases were generated during the proton collision. It is difficult to accurately measure the characteristics of Higgs particles. If the positive and negative electronic collision is used, the foundation is very low, which is conducive to the nature of the Higgs particles in a "clean" collision environment. In addition, positive and negative electronic collisions have a fixed quality heart -based energy. You can use Z Bigga to independently and accurately measure Higgs's generic scoop and decaying branch through ZH. The advantage. At present, there are three "Higgs Factory" solutions based on positive electronic collisions, Japan's international linear collision (ILC), China's high -energy ring positive electronic collision (CEPC), and Europe's future ring shape Cambrian (FCC).

7.1 Japan's ILC

ILC is a straight -line accelerator with a length of 30 kilometers. It performs positive and negative electronic collisions. The quality of the quality of the quality can reach 500 GEV or higher. Gus auto -coupled, etc. The construction of ILC involves a large number of advanced accelerator technology and detector technology. Although ILC costs expensive and risky construction process, considering the extremely significant scientific significance of ILC, the founding country is hopeful to become a new hegemon in the field of particle physics. European CERN, Fermilab, Fermilab and Japan's high -energy accelerator research institutions, all show great interest in the construction of ILC. After years of pre -research and competition, the international high -energy physics community finally formed a consensus to support Japan's ILC project. The international preparation group (IDT) was established in 2020, and China was excluded from the United States. In 2021, Japan established the ILC project development center, and various tasks are steadily promoting. It is expected that the pre-laboratory (Pre-Lab) will be established in the next 3 to 4 years. See Figure 9.

Figure 9 International linear collision machine ILC schematic diagram

7.2 China's CEPC

The discovery of Higgs particles also greatly inspired the high -energy physics community in China. Carefully analyzed the development situation in the field of high -energy particles in the international high -energy particle physics. The United States has lost its leading position in the field of high -energy physics due to the reduction of funds in the United States. Europe took this opportunity to surpass the United States as a new leader. Running and upgrading, Japan is busy with the construction of ILC projects. China has a rare opportunity that can make full use of China's advantages and use mature ring accelerator technology to build the next generation of the Higgs factory based on ring -shaped positive and negative electronics collisions in China, so as to make China's high -energy accelerator and Graval detector technology has achieved a large leap development, leading the forefront of international high -energy physical experimental research. From September 13th to 14th, 2012, just two months after the discovery of Higgs particles, the China High Energy Physical Society held a "2nd China High -Energy Accelerator Physics Strategic Development Seminar" in Beijing, from more than 40 from all over the country. Experts and scholars participated in the seminar, and for the first time at the seminar, the grand idea of ​​building the next generation of ring -shaped positive and negative electronic collision CEPC in China, that is, first build a period of about 50 to 100 kilometers per week and 240 GEV energy for 240 GEV. The ring -shaped positive and negative electronic collision machine is used as the Higgs factory; in the future, it can be transformed into a super proton collision with energy 50 ~ 100 TEV in the same tunnel in the future. The energy will be about 6 times higher than the running LHC. To achieve the ultimate goal of future accelerators. CEPC is aimed at the core frontier physical problems of Higgs particles after discovery. Its scientific goal is to accurately measure the nature of Higgs particles and explore the more basic physical laws behind the standard model. Subsequently, the domestic high -energy physics community organized a research team to conduct pre -research in the early stage of CEPC.

In February 2014, the forum was held in Beijing after the "Higgs particle discovered, where the basic physics developed" in Beijing. Internationally renowned physicists such as the winner of the prize. The guests firmly believe that the next generation of particle accelerators will bring important breakthroughs to the world, and believe that CEPC will start the opportunity to become a world leader in the field of particles and accelerators in the field of physical physics. The Nobel Prize winner David GROSS believes that China ’s next -generation accelerator CEPC proposed to build will make China at a central position in the field of basic science. He said: "I call this dream a Chinese accelerator, which will be as remarkable as the Greatwall. And discovery. "

After 6 years of hard work, in November 2018, the CEPC research team officially released the two -volume concept design report of accelerators, physics and detectors. Multi -page design report. See Figure 10 CEPC concept design drawing. The future of particle physics is very clear. In the next few decades, the nature of Higgs particles has been a consensus of the world's high -energy physics community, and the collision machine designed by China is almost the best choice for cost and efficiency.

Figure 10 high -energy ring positive and negative electronic collision CEPC schematic diagram

7.3 European FCC

After publishing its own Higgs particle plant collision in China, the European Nuclear Research Center also released the "Future Circle collision" (FCC) they designed in 2019. Figure 11. However, without the expectations of scientists, the European FCC design on some key indicators in the positive electronic collision stage is "almost the same" as China's CEPC design, because this is the optimal solution to study Higgs physics.

FIG

In June 2020, the European particle physics strategic plan clearly clearly listed the positive and negative electron collision Higgs factory as the highest priority next -generation high -energy physical accelerator facilities and layouts and invested large -scale technology research and development. It can be seen that the current efforts of particle physicists around the world are consistent. However, CERN, the European Nuclear Research Center, is still running a large -scale strong collision LHC, and in the next 15 to 20 years, Europe also plans to upgrade the LHC multiple times. These plans will restrict the FCC construction plan. China and China It is expected to build the Higgs particle factory in the ten years earlier than Europe, thus winning the opportunity in fierce international competition.

08

Conclusion

China in the 21st century is struggling to achieve the "two hundred years" goal and the Chinese dream of the great rejuvenation of the Chinese nation. Chinese scientists must provide strong scientific and technological support for the realization of the Chinese dream, make China a great scientific and technological innovation country, and provide strategic support for improving social productivity and comprehensive national strength. The development of Chinese science and technology will face the new direction of the world's forefront and national strategic needs, and make a new direction of science and technology breakthroughs, and make great contributions to basic, strategic and original.

After the discovery of Higgs particles, the CEPC Higgs factory carried the expectations and dreams of Chinese high -energy physicists, which is also an important part of realizing the "Chinese dream" of the great rejuvenation of the Chinese nation. Building an international science city with CEPC as the core has enabled China to achieve leapfrog development in key technologies such as basic physics research, accelerators and detectors. From the transition from runners to runners, and eventually becoming the leader of the world. This is a rare historical opportunity for national development. Its important scientific significance, the major impact of the international development, and the promotion role on China's future development are irreplaceable. Due to fierce international competition, this historical opportunity time window is less than ten years. This is the heavy responsibility given to this generation. I sincerely look forward to this dream can become a reality, so that "China's big accelerator" is as eye -catching as the Great Wall of Wanli. When the 100th anniversary of the founding of the People's Republic of China, it really plays a role in leading the future. (End) This article was reproduced from WeChat public account with authorization: Modern Physical Knowledge Magazine Author: Chen Yongzhen Yang Haijun

Reprinted content only represents the author's point of view

It does not represent the high energy office of the Chinese Academy of Sciences

Edit: Yang Yang

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