Quark (English: quark, Japanese: ク ォ ー ク, Korean: 쿼, Greek: Quark, Hebrew: Quark, Russian: Кварковые, Thai: ภ, ู, ฐ, ส, ช, French Arabic: ك, و, A proton collides with an antiproton at high energy, producing a pair of almost free quarks.All neutrons are composed of three quarks, and antineutrons are composed of three corresponding antiquarks, such as protons and neutrons.Protons are composed of two upper quarks and one lower quark, while neutrons are composed of two lower quarks and one upper quark.Quark theory is a theory that studies the properties of quarks.
Have you all heard of atoms?Those smaller than atoms have protons and neutrons, those smaller than protons and neutrons have photons and electrons, and those smaller than photonic electrons are called quarks.
Theory presentation
In the 1960s, American physicistsMurray GelmanandG. ZweigThe neutrons and protons are proposed independentlyhadronIt is composed of more basic units——quarkMany Chinese physicists call it "straton".They have a fractional charge, which is 2/3 or - 1/3 times the electric quantity of the electron, and a spin of 1/2.The word quark isGelmanderive fromJ. JoyceThe phrase in Finnegan's All Night Sacrifice is "for Mark the Reviewer King, three voices of quark".Quark has many meanings in the book, one of which is the call of a seabird.He believes that this is suitable for his original strange idea that "the basic particles are not basic, and the basic charge is not an integer". At the same time, he also points out that this is just a joke, which is against the pretentious scientific language.In addition, it may also be the reason why he likes birds.
theoretical explanation
The initial explanation of hadron interacting particles requires three theoriesquarkThe three flavors called quarks areUpper quark(up,u)、Lower quark(down, d) andStrange quark(strange, s). In 1974, J/ψ particles were discovered, requiring the introduction of a fourth quark:Charm quark(Charm, c). The gamma particle was discovered in 1977, requiring the introduction of a fifth quark:Bottom quark(bottom,b)。
The sixth quark was discovered in 1994:Top quark(top, t), which is believed to be the last quark.Quark theory holds that allbaryonThey are all composed of three quarks, and antibaryons are composed of three corresponding antiquarks.For example, 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, called a negative ω particle.
classification
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Quarks are divided into three generations according to their characteristics, as shown in the table below:
Symbol Chinese name English name Charge (e) Mass (GeV/c ^ 2)
U upper quark up+2/3 0.004
D Lower quark down - 1/3 0.008
C Charm quark charm+2/3 1.5
S strange quark - 1/3 0.15
T top quark top+2/3 176
B Bottom quark - 1/3 4.7
In quantum chromodynamics, quarks not only have the characteristics of "taste", but also have the characteristics of three "colors", namely red, green and blue.Here, "color" does not mean that quarks really have color, but that they use the word "color" to describe a physical property of quarks themselves.Quantum chromodynamicsIt is believed that general matter has no "color", and the "colors" of the three quarks that make up baryons are red, green and blue, so they are colorless when added together.Therefore, taking into account the attributes of 6 flavors and 3 colors, there are 18 kinds of quarks, and 18 kinds of anti quarks corresponding to them.
Quark theory also believes that,mesonIt is a bound state composed of a quark and an antiquark of the same color.For example, the [[π+meson]] predicted by Japanese physicist Hideki Tanagawa is composed of an upper quark and an anti lower quark, and the π - meson is composed of an anti upper quark and a lower quark, both of which are of the same color.
In addition to the top quark, five kinds of quarks have been found to exist through experiments, and Ding Zhaozhong, a Chinese scientist, was rewarded with the discovery of charm quarkThe nobel prize in physics。In recent ten yearsHigh-energy particleOne of the main directions of physicists 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 the quarkon, which is helpful to study how the universe evolves within less than one second at the beginning of the Big Bang, because the high heat generated at the beginning of the Big Bang will produce top quark particles.
Related research
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Research shows that some stars may become "quark stars" at the end of their evolution.When a star cannot withstand its own gravitational force to shrink, the density will increase greatly, squeezing out quarks. Finally, a star the size of the sun may shrink to only seven or eight kilometers, but it will still emit light.
Quark theory holds that quarks are trapped inside particles, and there is no single quark.Some people objected that quarks do not really exist.However, almost all predictions made by quark theory are in good agreement with experimental measurements, so most researchers believe that quark theory is correct.
In 1997, Russian physicist Diakonov and others predicted that there was a particle composed of five quarks with a mass 50% larger than that of hydrogen atom.In 2001, Japanese physicists found evidence of the existence of five quark particles when they bombarded a piece of plastic with gamma rays on the SP-8 accelerator.Subsequently, it was confirmed by physicists from Thomas Jefferson National Accelerator Laboratory and Moscow Institute of Theoretical and Experimental Physics.This five quark particle is composed of two upper quarks, two lower quarks and an anti strange quark, which does not violate the standard model of particle physics.This is the first time to find a particle composed of more than three quarks.Researchers believe that this particle may only be the first discovered member of the "five quark" particle family, and there may be particles composed of four or six quarks.
To correct it, some people say that the discovery of quarks is totally a nonsense without understanding science. Now human beings are just bold assumptions and scientific verification. Quarks are possible hypotheses put forward to explain some phenomena that human beings cannot explain at present, but human beings have never found direct evidence for the existence of quarks.On December 2, 1996, Science and Technology Daily publishedCui JundaProfessor refuted Academician He Zuoma's article "Complex space-time theory is not pathological science".Cui Zaiwen further pointed out that "not all physicists recognize the existence of quarks. Disagreements have existed since the 1970s. Chinese physicist Zhu Hongyuan, Nobel laureate and founder of quantum mechanics Heidelberg all believe that many physicists around the world have spent so much effort to find quarks. If quarks really exist, they should have been found long ago."
The scientist is certainly wrong to deny quarks in this way. For example, the saying "if quarks really exist, they should have been found long ago" is obviously a fallacy, which means that "if Goldbach's conjecture can be proved, it should have been proved long ago".
In short, science should not be a little false and emotional.Quarks cannot directly prove its existence, nor can they prove (even indirectly) that it does not exist. It is only a hypothesis at present.[1]
