Taylor, a Canadian, received his B.Sc. in 1950, his M.Sc. in 1652, his Ph.D. in 1962 at Stanford, and he became an associate professor at Stanford's Linear Accelerator Center in 1968 and was promoted to professor in 1970. American Friedman received his B.S. in 1950, M.S. in 1953, and Ph.D. in 1956 from the University of Chicago. He came to the Massachusetts Institute of Technology as an associate professor in 1960, was promoted to professor in 1967, and served as chairman of the physics department at the institute from 1983-1988. Kendall, an American, received his bachelor's degree from Amherst College in 1950, his Ph.D. in physics from MIT in 1954, and two years later became an associate professor at Stanford, and a professor at MIT in 1967．
The experiments performed at the Stanford Linear Accelerator Center are similar to those performed by E. Rutherford to verify the nuclear model of the atom. Just as Rutherford predicted the existence of a nucleus in the atom due to the observation of large numbers of alpha particles scattered at large angles, the Stanford Linear Accelerator Center confirmed the existence of a point-like component in the structure of the nucleus, which is now understood to be quarks, by the unexpected scattering of large numbers of electrons at large angles.
The existence of quarks was predicted by M. Gell-Mann in 1964, and independently by G. Zweig of the California Institute of Technology (Caltech) at the same time. Before the experiments at the Stanford Linear Accelerator Center - MIT, no one had been able to come up with convincing kinetic experiments to confirm the existence of quarks in protons and neutrons. In fact, the role of quarks in hadron theory was unclear to theorists at that time. As C. Jarlskog said when introducing the winners to the King of Sweden at the Nobel ceremony, "The quark hypothesis was not the only hypothesis at that time. There was, for example, a model called 'nuclear democracy' which argued that no particle could be called a fundamental unit and that all particles were equally fundamental and constituted each other."
In 1962 Stanford began construction of a large linear gas pedal with an energy of 10-20 GeV, which, after a series of improvements, could reach 50 GeV. Two years later, W. Panofsky, director of the Stanford Linear Accelerator Center, was supported by several young physicists who had worked with him when he was the director of the Stanford High-energy physics laboratory director and he **** work, Taylor is one of them, and served as an experimental group leader. He was soon joined by Friedman and Kendall, then faculty members at MIT, who had been doing electron scattering experiments at the 5 GeV Cambridge Electron Accelerator, a cyclotron with limited capacity. But at Stanford there would be a 20 GeV gas pedal that could produce "absolutely strong" beams, high current densities, and external beams. A team from the California Institute of Technology has also joined the collaboration, and their main task is to compare electron-proton scattering with positron-proton scattering. A large team of scientists from the Stanford Linear Accelerator Center, the Massachusetts Institute of Technology and the California Institute of Technology (this team is called Group A). They decided to build two spectrometers, a large-acceptance spectrometer at 8 GeV and a small-acceptance spectrometer at 20 GeV. The new design of the spectrometers differed from the earlier spectrometers in that they were focused horizontally at a single point in a straight line, rather than point by point as in the old equipment. This new design allows the scattering angle to spread out horizontally and the momentum to spread out vertically. Momentum can be measured to 0.1 percent, and scattering angles can be accurate to 0.3 milliradians.
At that time, the mainstream of physics believed that protons had no point-like structure, so they expected the scattering cross section to decrease rapidly with q2 (q is the four-dimensional momentum imparted to the nucleon). In other words, they expected that large-angle scattering would be rare, and the experiments turned out to be unexpectedly large. In their experiments, they used a variety of theoretical assumptions to estimate the count rate, none of which included histone particles. One of these assumptions used the structure function observed in elastic scattering, but the experimental results differed from the theoretical calculations by one to two orders of magnitude. This is an amazing discovery, and one wonders what it means. No one in the world (including the inventor of quarks and the entire theoretical community) said specifically and definitively, "You go look for quarks, I believe they are in the nucleus." In this context, J. Biorken, a theorist at the Stanford Linear Accelerator Center, came up with the idea of calibration irrelevance. While still a graduate student at Stanford, he completed a study of inelastic scattering kinematics with L. Hand. When Bjorken returned to Stanford in February 1965, he was naturally drawn to the subject of electrons by his environment. He remembered that in 1961 at the Stanford colloquium, listening to Schiff (L-Schiff) said that inelastic scattering is the study of the instantaneous charge distribution in the proton, the theory explains how the inelastic scattering of electrons gives the momentum distribution of neutrons and protons in the nucleus. At that time, Gell-Mann introduced flow algebra into field theory, discarding some of the errors in field theory while maintaining the convective relations of flow algebra. S. Adler derived the summation rules for neutrino reactions by means of a fixed field flow algebra. Bjorken spent two years studying high-energy electron and neutrino scattering using flow algebra in order to calculate the integral of the structure function over the entire summation rule and to find the shape and size of the structure function. The structure functions W1 and W2 are in general functions of two variables. These two variables are the square of the four-dimensional momentum transfer q2 and the energy transfer v. Bjorken then argues that the structure function W2 depends only on the acausal ratio ω = 2Mv/q2 (M denotes the mass of the proton) of these variables, i.e., vW2 = F(ω), which is Bjorken's scalar irrelevance. In arriving at the scalar irrelevance, he used many parallel methods, the most ponderous of which is the point structure. The summation rules of the flow algebra imply pointwise structure, but do not require it. However, Bjorken naturally derived the scalar irrelevance of the structure function from this implication, in combination with some other notions of strong interactions such as Regge poles that make the summation rules converge.
When calibration irrelevance was proposed, many people were not convinced. As Friedman said: "These ideas were put forward, we do not fully confirm. He was a young man, and we felt that his ideas were amazing. We didn't expect to see point structures, and what he was saying was just a lot of nonsense." In late 1967 and early 1968, experimental data on deep inelastic scattering had begun to accumulate. When Kendall showed Bjorken the new analysis of the data, Bjorken suggested that the data be analyzed in terms of a scale-independent variable, ω. Following the old method of plotting, Kendall said, "The data are so scattered that they cover the coordinate paper like a chicken's paw prints. When the data were processed by Bjorken's method (vW2 vs. ω), they were brought together in a powerful way. I remember how Balmé felt at the time when he discovered his empirical relation - the wavelengths of the hydrogen spectrum were fitted with absolute precision." In August 1968, at the 14th International Conference on High Energy Physics, Friedman reported the first result, and Pannowsky, as leader of the conference, hesitantly raised the possibility of a point-like structure of the nucleus.
When data on 6° and 10° scattering were collected from the 20 GeV spectrometer, Group A proceeded to do 18°, 26°, and 34° scattering with the 8 GeV spectrometer. Based on these data it was found that the second structure function W1 is also a function of a single variable ω, i.e., obeys the Bjorken scale-independence. The results of all these analyses remain correct until today, and even after more precise radiative corrections, the difference in the results is not greater than 1%. Beginning in 1970, experimenters performed similar scattering experiments with neutrons, in which they alternated between hydrogen (protons) and deuterium (neutrons) for one hour each to minimize systematic errors.
As early as 1968, R. Feinman of the California Institute of Technology had already thought that the hadron was composed of smaller "partons". When he visited the Stanford Linear Accelerator Center in August of the same year, he saw the data on inelastic scattering and the Bjorken scale dependence. Feinman believed that the partons were in the high-energy relativistic nucleus
That is, the structure function was correlated with the momentum distribution of the partons. This is a simple kinetic model, another way of saying the Bjorken view. Feinman's work greatly stimulated theoretical work, and several new theories appeared. After Kellan (C-Gllan) and Gross (D-Gross) derived a close correlation between the ratios R of W1 and W2 and the parton spins, the Stanford Linear Accelerator Center-MIT
Feinman's requirements for quarks, thus eliminating other assumptions. Analysis of the neutron data clearly shows that the neutron yield is different from the proton yield, which further disproves other theoretical assumptions.
A year later, neutrino inelastic scattering done in the heavy-bubble chamber at CERN provided a powerful extension of the experimental results at the Stanford Linear Accelerator Center. In order to take into account the difference between electromagnetic interactions between quarks and weak-flow interactions between neutrinos, the Stanford Linear Accelerator Center pair was brought
into full conformity with the Stanford Linear Accelerator Center data. Later muon deep inelastic scattering, electron-positron collisions, proton-antiproton collisions, and hadron injection all show quark-quark interactions. All of them provide strong evidence for the quark structure of the hadron.
It took years for the physics community to accept quarks, largely due to the contradiction between the point-like structure of quarks and their strong confinement in the hadron. As J?rskog said at the Nobel ceremony, quark theory does not explain the experimental results completely and uniquely, and the experiments that won the Nobel Prize showed that protons also contain electrically neutral structures, which were soon discovered to be "gluons". Among protons and other particles, gluons glue quarks together. 1973 saw the independent discovery of the asymptotically free theory of non-abelian canonical fields by Gross, F. Wilczek and H. D. Politzer. This theory states that if the interactions between quarks are induced by color-canonical gluons, the couplings between quarks weaken logarithmically at short distances. This theory (later called quantum chromodynamics) easily explains all the experimental results at the Stanford Linear Accelerator Center. In addition, the opposite of asymptotic freedom, the increase in the strength of the coupling at long distances (called infrared slavery) accounts for the mechanism of quark confinement. The father of quarks, Gell-Mann, said in 1972 at the 16th International Conference on High Energy Physics, "Theory does not require that quarks be truly measurable in the laboratory; at this point like magnetic monopoles, they can exist in the imagination." In short, electron inelastic scattering experiments at the Stanford Linear Accelerator Center show the point-like behavior of quarks, which is the experimental basis for quantum chromodynamics.
Quark
quark
In the 1960s, American physicists Murray Gell-Mann and G. Zweig each independently proposed that the category of hadrons, the neutron and proton, is composed of more fundamental units, quarks (quarks), which many Chinese physicists call "laminons". They have a fractional charge, 2/3 or -1/3 times the electron's charge, and a spin of 1/2.The term quark was taken by Gell-Mann from the words "Three quarks for the king of the Mark reviewers," in J. Joyce's novel Finneganson All-Night Sacrifice. Quark has a number of meanings in the book, one of which is the call of a seabird. He thought it suited his original peculiar idea that "elementary particles are not elementary and elementary charges are not integers", but he also pointed out that it was just a joke, a revolt against the pretentious language of science. Also, it may be why he likes birds.
The original theory explaining strongly interacting particles required three kinds of quarks, called the three flavors of quarks, which are up quarks (up,u), down quarks (down,d), and strange quarks (strange,s).The discovery of the J/ψ particle in 1974 called for the introduction of a fourth kind of quarks the charm quarks (charm quarks) (charm,c).The discovery in 1977 of the Υ particle, requiring the introduction of a fifth quark, the bottom quark (bottom,b). 1994 saw the discovery of a sixth quark, the top quark (top,t), which is believed to be the last quark.
Quark theory states that all baryons are made up of three quarks, and antibaryons are made up of three corresponding antiquarks. For example, the proton (uud), and the neutron (udd). Quark theory also predicts the existence of a particle made of three exotic quarks (sss), which was observed in a hydrogen bubble chamber in 1964, called the negative ω particle.
Quarks are divided into three generations according to their properties, as shown in the following table:
Symbol Chinese name English name Charge (e) Mass (GeV/c^2)
u up up quark up +2/3 0.004
d down quark down -1/3 0.008
c charm charm +2/3 1.5 <
s strange quark strange -1/3 0.15
t top quark top +2/3 176
b bottom quark bottom -1/3 4.7
In quantum chromodynamics, quarks, in addition to their "flavor" properties, have three other "color" properties, which are red, green, and blue. Here "color" does not mean that quarks really have colors, but the word "color" is used as a metaphor for a physical property of quarks themselves. Quantum chromodynamics suggests that matter in general has no color, and that the three quarks that make up the baryon have the "colors" of red, green, and blue, making them colorless when stacked together. So taking into account the properties of 6 flavors and 3 colors, there are 18 quarks, and another 18 antiquarks corresponding to them.
Quark theory also suggests that mesons are bound states consisting of a quark of the same color and an antiquark. For example, the [[π+ meson]] predicted by Japanese physicist Hideki Yukawa is composed of an up quark and an anti-down quark, and the π-meson is composed of an anti-up quark and a down quark, both of which are colorless.
Five quarks other than the top quark have been experimentally discovered to exist, and Chinese-born scientist Ding Zhaozhong was awarded the Nobel Prize in Physics for his discovery of the charm quark. One of the main focuses of high-energy particle physicists in the last decade has been the top quark (t).
The discovery of the sixth "top quark" in 1994, believed to be the last, has given scientists a complete picture of quarks, which will help them study how the universe evolved in less than a second at the beginning of the Big Bang, when the initial heat of the Big Bang created top quark particles.
The study shows that some stars may become "quark stars" at the end of their evolution. When a star can't resist its own gravity and shrinks, its density increases so much that quarks are pushed out, and eventually a star the size of the sun may shrink to only seven or eight kilometers in size, but it will still shine.
Quark theory holds that quarks are all imprisoned inside particles and that there are no individual quarks. Some people have based their objections on this, arguing that quarks are not real. However almost all of the predictions made by quark theory fit well with experimental measurements, so most researchers believe quark theory is correct.
In 1997, Russian physicist Daiakonov and others predicted the existence of a particle consisting of five quarks, with a mass 50 percent greater than that of a hydrogen atom, and in 2001, Japanese physicists found evidence of the existence of a pentaquark particle when they bombarded a piece of plastic with gamma rays at the SP Ring-8 gas pedal. It was subsequently confirmed by physicists at the Thomas Jefferson National Accelerator Laboratory in the United States and the Institute of Theoretical and Experimental Physics in Moscow. This pentaquark particle is made up of 2 up quarks, 2 down quarks and an anti strange quark, and it does not violate the standard model of particle physics. This is the first time a particle consisting of more than three quarks has been found. The researchers believe that this particle may be only the first member of the "pentaquark" family of particles to be discovered, and that there may also be particles composed of four or six quarks.
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I'm going to amend that: some people say that the discovery of so-and-so quarks is completely unaware of the science of fabrication, and now human beings are only bold assumptions, scientific evidence, quarks are to explain some of the current human phenomena that can not be explained by the hypothesis of the possible existence of quarks. The quarks are a hypothesis to explain some phenomena that cannot be explained by human beings at present, but human beings have never found any direct evidence of the existence of quarks.
On December 2, 1996, Science and Technology Daily published Professor Cui Junda's rebuttal to Academician He Joma's article, "Compound Space-Time Theory is Not a Sick Science". In the article, Cui further pointed out that "not all in the physics community recognize the existence of quarks. Dissenting views have existed as early as the 1970s. Zhu Hongyuan, a physicist in China, and Heidelberg, a Nobel laureate and the founder of quantum mechanics, all thought that if quarks really existed, they should have been found a long time ago after so many physicists around the world had spent so much effort searching for them."
It's certainly not true that this scientist denies quarks, as in "If quarks really existed, they would have been found long ago."
In short, science is not about falsehoods and emotions, and quarks are not a direct proof that they exist, nor are they a proof (even indirectly) that they don't, they are just hypotheses at this point in time.