There's good news for the accelerator. 1949 discovered neutral pion, and later discovered positive and negative and neutral σ particles, negative and neutral ξ particles, neutrinos, antiprotons and antineutrons.
When I couldn't find new particles before, I tried my best to find them. Now I'm worried about such a big pile. People can't help but sigh Mendeleev's greatness. The great Mendeleev put all the elements in a table, which not only looks orderly, but also points out the laws between the elements. Can so many particles do it?
A young physicist asked Fermi this question. Fermi sighed. "Young man, if I remembered so many names, I would have become a botanist."
Fermi's sigh revealed the predicament at that time. Although the classification of botany is far less beautiful than the periodic table of elements, the classification of microscopic particles at that time could not even be as rough as botany. People just reluctantly divide these particles into fermions and bosons.
Fermions are particles that make up matter, including leptons and baryons. Leptons are light particles, including electron muons, neutrinos and their antiparticles. Baryons include proton neutrons, λ particles, σ particles, ξ particles and their antiparticles. Bosons are particles that transfer force, including photons and all mesons. Mesons and baryons make up hadrons. God, what a mess. Kind of like a botanical classification. Looks a little regular.
Throughout the history of science, physicists don't like this botanical classification, they prefer to find the origin of the world. Fermi and Yang Zhenning, the first model of hadron structure, believe that π mesons are composed of protons or neutrons and their antiparticles. When they put forward this statement, antimatter particles had not yet been discovered, which really required considerable courage and boldness.
Based on Marxist dialectical materialism, Japanese physicist Sakata Shyoichi thinks that proton neutrons and λ particles are the most basic particles of matter, and tries to construct other particles with them.
Oriental physicists are influenced by western philosophy, but what about western physicists? Naturally, they should be inspired by oriental philosophy. German found the "Eight Proverbs" mentioned by the Buddha very interesting, and put forward the "Eight States", which is basically the periodic table of elements of this pile of particles.
Gherman's octet is really beautiful. It not only classifies particles, but also predicts new particles like the periodic table of elements. Ω particles are predicted, but it is useless to have a periodic table. Mendeleev didn't understand why the periodic table of elements was arranged in this way. It was not until people understood the structure of the nucleus that they realized that it was arranged according to the number of protons and electrons outside the nucleus. Gherman explained the origin of the particle himself before others explained the octahedron this time.
Gherman put forward a new view of quarks. He said that quarks are divided into three kinds, and protons and neutrons are composed of three kinds of quarks. However, this leads to a problem. The charge number of a proton is 1, and three quarks make up a proton, so there will be a charge of 1/3. It's true. Gherman divided quarks into upper quarks, lower quarks and odd quarks. The upper quark has a band.
This sounds a little strange. In fact, gherman himself is not sure. He doesn't think such particles really exist. male
Call it "the product of mathematics". The proposer himself has no idea, let alone expect others to admit it, so for a long time, people thought it was nonsense.
If the theory is not clear, let's watch the experiment. Rutherford, the grandfather of that year, was deified by alpha particle scattering experiment, which also revealed the secret of atoms. Now the experiment is going to smash protons to see if it can be broken. But Rutherford's experiment had a gift of alpha particles from nature, but now it is gone. Since nature can't give it, do it yourself. This is an accelerator, which uses high-energy electrons to directly collide with protons.
This collision has three results. One is that table tennis hits the shot put and flies directly. The second result is that electrons excite protons, and both electrons and protons are still intact, that is, the energy of protons has changed, and a few new particles have been produced by the way. It's like a ping-pong ball hitting a shot put and a little dust flying. If the electron energy is enough, it is not impossible. There's another one.
However, the most unlikely result still appeared. The experimental results show that protons do have an internal structure, which means that protons can be subdivided, but are they divided into quarks? No one really understands this, because the mathematical description of Bjorcken, the initiator of the experiment, is too complicated, which is an obstacle for physicists. Physicists have never been good at mathematics, and Heisenberg agrees with this.
It seems that we have to ask for foreign aid after all. Foreign aid is the urchin Feynman. Feynman is enjoying the excitement of the Nobel Prize at this time, but he soon realized that honor can only represent the past, or should he make more contributions.
Feynman put forward the partial conjecture that hadron is composed of many parts. This is just a genius idea of his, and there is no experimental basis. However, the experimental results came to you. After seeing the experimental results, he shouted, "I have been looking for such an experiment all my life." After a night of thinking, Feynman explained the experimental results in concise and clear language, and people suddenly realized.
As for whether some protons are quarks? Feynman doesn't care. Genius doesn't care about these little things, which is similar to Paulie.
Later experiments proved that quarks did exist in protons, but the problem was bigger. Since there are quarks in protons and neutrons, why have you never seen free quarks? This is just one of the problems, and there are two other problems that the nascent quark theory could not solve at that time.
The first mountain in front of quark theory is Pauli, who is famous for his Pauli exclusion principle. This is not his only achievement, but his most important one. For microscopic particles, Pauli is like a king, and any particle must abide by his imperial edict. This is Pauli's exclusion principle.
According to the quark theory, quarks should be fermions with the spin of 1/2, and hadrons include two or more quarks with the same quantum state. For example, a proton consists of two upper quarks and a lower quark, and these two upper quarks are microscopic particles with the same quantum state, which violates the Pauli exclusion principle.
Experiments show that quarks in protons and neutrons wander freely like independent particles, but quarks are bound together by powerful nuclear forces. How can they hug each other and wander around? This is a problem that the second quark theory is difficult to explain.
These three problems have become three mountains in quark theory. The rice should be eaten bite by bite, and the mountains should be turned over one by one. Of course, Poly was the first mountain to be climbed. Who told him not to be provoked?
There are three ways to climb Poly Mountain. One is to prove that the Pauli exclusion principle is wrong. Nobody's ever done that. Einstein overthrew Sir Newton by demonstrating the nonexistence of ether, and achieved a generation of hegemony. The second method is to modify his own theory. There are precedents. At first Bohr thought there was something wrong with the law of conservation of energy, but Pauli thought there was no problem. He directly put forward the idea of neutrinos. As we said before, there is another trick. The charge spins of quarks are all the same, so add another degree of freedom. Doesn't that satisfy the Pauli exclusion principle without destroying our own theory? This is a happy thing.
Of course, gherman will do the best, but gherman is a little careless, because he just won the Nobel Prize, and he is not sure whether there is such a thing as quarks. However, some people are worried. This anxious person is Feric, and he is also a strange person. He comes from the GDR. At that time, Germany had not been unified, and Berlin had a long wall. In pursuit of knowledge, he secretly ran to the Federal Republic of Germany and began to study theoretical physics at the Planck Institute of Physics in Munich.
Feric came from a socialist country and was deeply educated by Marxism. He believes quarks must exist, and he doesn't understand gherman's casual attitude. When 1970 met gherman, he strongly expressed his confidence. People risk their lives in pursuit of the truth, so it is inappropriate for him to care about these. So, gherman began to ponder the new model with Feric.
They realized that they could solve the problem by adding a quantum number. What should they use? Up and down were used at first, but left and right can't be used this time. Besides, the left, right, up and down are all locative words, and you can't see any new ideas at all. Inspired by the French flag, Fermon decided to name the new quantum number by color. In fact, this is nothing new. Feynman has used colors to refer to different neutrinos. No matter how much, quarks in the new quark scheme may have three colors, namely red, white and blue, which is the color of the French flag. However, the name of this color is a bit unscientific, and later it was changed to the three primary colors of blue, red and green, because in this case, three quarks together will turn white, that is, the quantum number is zero, so proton neutrons do not have this quantum number. However, it should be noted that the "color" of quarks is not really a colored quark, it is just a synonym and title of quantum freedom.
Now Paulie's problem is solved. Protons consist of a blue upper quark, a red upper quark and a green lower quark. Neutron consists of a blue upper quark, a red lower quark and a green lower quark. There are no quarks with exactly the same quantum number, and the number of quarks has tripled.
Now let's look at the next question, how quarks wander freely inside hadrons and hold groups together. In our general impression, the closer they are, the greater the attraction, and so is the electromagnetic force. From this point of view, quarks really can't wander at will, but they can only hug each other tightly, but quarks don't rely on gravity and electromagnetic force. They rely on nuclear power. Through experiments and analysis, it is found that the nuclear force between quarks has a special property, that is, asymptotic freedom. Simply put, the closer you are, the smaller the nuclear force is, and you can wander around. The farther you are, the greater the nuclear force is, and it looks like a proton. Well, finally, another problem has been solved.
Let's look at the ultimate problem. This is the quark confinement problem Why have you never seen a quark? Just now I talked about an asymptotic freedom. With the increasing distance between quarks, the nuclear force is also increasing. Does this explain quark confinement? It is because the nuclear force is getting bigger and bigger that quarks can't fly out, but we can increase energy and surpass the nuclear force. Why can't we see a single quark?
There is no good explanation for this at present, and there is speculation that it is. With the increasing energy, just as quarks are about to fly out, this energy is large enough to appear a pair of positive and negative quarks in a vacuum. The antiquark will immediately pair with the flying quark to form a meson, and another quark will immediately replace the original quark in hadron.
Anyway, quark theory has been established, but it's not over yet. It's time for China people to take the stage.