What is the smallest particle found so far?

in quantum field theory, a * * * has three kinds of fields and 62 kinds of particles. The first kind of physical particle field includes 48 kinds of particles, including leptons and quarks. An electron is a lepton. Although quarks are inseparable now, there is a subtle correspondence between leptons and quarks. People divide them into three generations:

the first generation: upper quarks and lower quarks

the second generation: odd quarks and charm quarks

the third generation: top quarks and bottom quarks

and leptons include electron neutrinos

among all the 62 particles.

quark

quark

In the 196s, American physicists Murray gherman and G. Zweig independently proposed that hadrons such as neutrons and protons are composed of quarks, a more basic unit, which many Chinese physicists call "stratons". They have fractional charge, which is 2/3 or -1/3 times as much as that of electrons, and their spin is 1/2. Quarks are a phrase taken by gherman from J Joyce's novel "A Night Sacrifice in finnigan". Quarks have many meanings in this book, one of which is the cry of a seabird. He thinks that this is suitable for his initial thought that "basic particles are not basic, and elementary charge". At the same time, he also pointed out that this is just a joke, which is a resistance to the pretentious scientific language. In addition, it may be the reason why he likes birds.

The original theory of explaining strongly interacting particles requires three kinds of quarks, which are called the three flavors of quarks, namely the upper quark (up,u), the lower quark (down,d) and the strange,s quark (s). J/ψ particle was discovered in 1974, and it is required to introduce the fourth quark (charm,c). In 1977, the particle υ was discovered, and the fifth quark bottom (B) was required to be introduced. The sixth quark top,t quark (T) was discovered in 1994, which is believed to be the last quark.

quark theory holds that all baryons are composed of three quarks, and anti-baryons are composed of three corresponding antiquarks. Such as protons (uud) and neutrons (udd). Quark theory also predicted the existence of a particle (sss) composed of three strange quarks, which was observed in the hydrogen bubble chamber in 1964 and called negative ω particle.

quarks are divided into three generations according to their characteristics. As shown in the following table:

symbol Chinese name English name charge (e) mass (GeV/C 2)

quark up+2/3.4

quark down -1/3 .8

c charm quark charm+2/31.5. 3 .15

t-top quark top +2/3 176

b-bottom quark bottom -1/3 4.7

In quantum chromodynamics, quarks have three "color" characteristics besides "taste", namely red, green and blue. Here, "color" does not mean that quarks really have color, but the word "color" is used to vividly compare a physical property of quarks themselves. Quantum chromodynamics holds that there is no "color" in general matter, and the "colors" of the three quarks that make up baryons are red, green and blue respectively, so they are colorless when superimposed together. Therefore, taking into account the attributes of six flavors and three colors, * * * has 18 quarks and their corresponding 18 antiquarks.

Quark theory also holds that mesons are bound states composed of a quark and an antiquark of the same color. For example, Japanese physicist Hideki Yukawa predicted that [[π+meson]] is composed of an upper quark and an anti-lower quark, while π-meson is composed of an anti-upper quark and a lower quark, which are colorless.

Five quarks except the top quark have been discovered by experiments, and Ding Zhaozhong, a Chinese scientist, won the Nobel Prize in physics for discovering charm quarks. One of the main directions of high-energy particle physicists in recent ten years is the top quark (T).

As for the sixth "top quark" newly discovered in 1994, it is believed to be the last one. Its discovery enables scientists to get a complete picture of quarks, which is helpful to study how the universe evolved in less than one second at the beginning of BIGBANG, because the high heat generated at the beginning of the Big Bang will produce top quark particles.

Research shows that some stars may become "quarks" at the end of evolution. When a star can't resist its gravitational contraction, the quarks will be squeezed out by a large increase in density. Eventually, a star the size of the sun may shrink to only seven or eight kilometers, but it will still shine.

quark theory holds that quarks are all trapped inside particles, and there is no single quark. Some people object that quarks don't really exist. However, almost all the predictions made by quark theory are in good agreement with experimental measurements, so most researchers believe that quark theory is correct.

in p>1997, Russian physicist Diane Konov and others predicted that there was a particle composed of five quarks, the mass of which was 5% greater than that of hydrogen atom. In 21, when Japanese physicists bombarded a piece of plastic with gamma rays on the SP Ring-8 accelerator, they found evidence of the existence of pentaquark particles. Later, it was confirmed by physicists at Thomas Jepperson National Accelerator Laboratory and Moscow Institute of Theoretical and Experimental Physics. This pentaquark particle is composed of two upper quarks, two lower quarks and an anti-singular quark, which does not violate the standard model of particle physics. This is the first time that particles composed of more than three quarks have been found. Researchers believe that this particle may be only the first member of the "five quarks" particle family to be discovered, and there may be particles composed of four or six quarks.

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > Let me correct it: Some people say. However, human beings have never found direct evidence of quarks.

On December 2, 1996, Science and Technology Daily published Professor Cui Junda's article "The Theory of Composite Space-time is not pathological science". Cui further pointed out in the article: "The existence of quarks is not universally recognized in physics. Disagreement dates back to the 197s. Zhu Hongyuan, a Chinese physicist, and Heidelberg, the Nobel Prize winner and founder of quantum mechanics, all think that many physicists all over the world have spent so much effort to find quarks. If quarks really existed, they should have found them long ago. "

It is certainly wrong for the scientist to deny quarks so much, like the sentence "If quarks really existed, they should have been found long ago." Obviously, it's a fallacy, which means that "if cancer really existed, it should have been cured long ago"

In short, science can't be false and emotional at all. Quarks can't directly prove its existence, nor can they prove (even indirectly) that it doesn't exist. It's just a hypothesis at present.