Gamma meson

The tasteless meson discovered by Leon Ledman in 1977

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Gamma meson (ϒ) is a tasteless meson composed of the bottom quark and its antiparticles. It was discovered by E288 of Fermi National Accelerator Laboratory in 1977, and its leader was in 1988 The nobel prize in physics Winner Leon Ledman. This is also the first discovered ion containing bottom quarks, because it is the lightest and does not need other ions of large mass to generate.

Chinese name: Gamma meson
Foreign name: Upsilon meson

Discovery time: 1977
Author: Leon Ledman
Role: This is the first ion found to contain bottom quarks.

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Gamma meson (ϒ) Bottom quark And its Antiparticle Tasteless meson 。 It is composed of Fermi National Accelerator Laboratory Of E288 Collaboration Discovered in 1977, the leader was in 1988 The nobel prize in physics winner Leon Ledman 。 This is also the first discovered ion containing bottom quarks, because it is the lightest and does not need other ions of large mass to generate. its average life span 1.21 × 10 -20 s , the mass is about 9.46 GeV/ c two 。^[1]

Bottom quark

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Bottom quark Yes with charge −1⁄ three The third generation of e quark , also known as Mequark 。 Although quantum chromodynamics describes each kind of quark in a similar way, because the bottom quark has a large Naked mass (Approx. 4.2 GeV/ c2 , slightly more than proton Four times the mass), and CKM matrix Elements of V ub And V cb The value of is very small, so the bottom quark has a unique label. As an experiment, a method called Bottom sticker Its trace can be easily identified by the technology of. because CP damage Three generations of quarks are involved, so the particles suitable for studying CP violation are those containing bottom quarks meson 。 BaBar experiment 、 Belle experiment And LHCb Experiments of this kind are being carried out.

Almost all Top quark The decay of, Higgs boson The decay of quarks also often produces bottom quarks. In 1973, to explain CP damage , Physician Kobayashi Cheng And Toshihide Maskawa Predict the existence of bottom quarks. Heim Harari The particle was named bottom quark in 1975. Fermilab Of Leon Ledman The research team made it through particle collision experiment in 1977 Bottom quarkonium To discover the bottom quark. For "discovering the source of symmetry breaking and predicting the existence of at least three kinds of quarks in nature", Kobayashi Shing and Yoshikawa Minying won the award in 2008 The nobel prize in physics 。 Some scholars call the bottom quark "beautiful quark", but so far, "bottom quark" is still the most commonly used name.^[1]

Antiparticle

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Antiparticle Compared with normal particles, their quality 、 life 、 spin Are the same as normal particles, but all internal additive quantum numbers (such as charge 、 Baryon number 、 Singular number And so on) are the same size as the normal particles and the symbols are opposite. There are some particles whose internal additive quantum numbers are all 0. Such particles are called pure neutral particles, and antiparticles are themselves, such as photon 、 Pion Etc. Not at all Particle physics Every particle in has an antiparticle in this sense, neutrino There would be no antiparticle, Antineutrino The definition of is different.

The concept of antiparticle was first introduced by British physicist Dirac in 1928 Hole theory Proposed in. In 1932 cosmic rays The discovery of positrons in confirmed Dirac's prediction. 1956 American physicist Owen Chamberlain (Owen Chamberlain) Lawrence Berkeley National Laboratory Antiproton was found. Further research found that Dirac's Hole theory yes Boson Not applicable, so it cannot explain all particles and antiparticles. According to quantum field theory, particles are regarded as the excited states of fields, and antiparticles are the complex conjugate excited states corresponding to such excited states.^[1]

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Oops-Leon In 1976, a similar particle with lighter mass was wrongly reported.
Quarkonium , by quark And the corresponding anti quark.
φ The particles are Odd quark The analogous state of.
J/ψ The particles are Charm quark The analogous state of.

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