MESONS:
Mesons are hadronic subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometre, which is about 2⁄3 the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Charged mesons decay (sometimes through intermediate particles) to form electrons and neutrinos. Uncharged mesons may decay to photons.
HADRON:
hadron is a composite particle made of quarks held together by the strong force (in the same way as atoms and molecules are held together by the electromagnetic force).
Hadrons are categorized into two families:
Hadrons are categorized into two families:
- baryons, such as protons and neutrons, made of three quarks
- mesons, such as pions, made of one quark and one antiquark.
Other types of hadron may exist, such as tetraquarks (or, more generally, exotic mesons) and pentaquarks (exotic baryons), but no current evidence conclusively suggests their existence.
BARYON:
A baryon is a composite subatomic particle made up of three quarks (as distinct from mesons, which comprise one quark and one antiquark). Baryons and mesons belong to the hadron family, which are the quark-based particles. The name "baryon" comes from the Greek word for "heavy", because, at the time of their naming, most known elementary particles had lower masses than the baryons.
As quark-based particles, baryons participate in the strong interaction, whereas leptons, which are not quark-based, do not. The most familiar baryons are the protons and neutrons that make up most of the mass of the visible matter in the universe. Electrons (the other major component of the atom) are leptons. Each baryon has a corresponding antiparticle (antibaryon) where quarks are replaced by their corresponding antiquarks. For example, a proton is made of two up quarks and one down quark; and its corresponding antiparticle, the antiproton, is made of two up antiquarks and one down antiquark.
Until recently, it was believed that some experiments showed the existence of pentaquarks — "exotic" baryons made of four quarks and one antiquark.
LEPTONS:
A lepton is an elementary, spin-1⁄2 particle that does not undergo strong interactions, but is subject to the Pauli exclusion principle.[1] The best known of all leptons is the electron, which governs nearly all of chemistry as it is found in atoms and is directly tied to all chemical properties. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons), and neutral leptons (better known as neutrinos). Charged leptons can combine with other particles to form various composite particles such as atoms and positronium, while neutrinos rarely interact with anything, and are consequently rarely observed.
There are six types of leptons, known as flavours, forming three generations.[2] The first generation is the electronic leptons, comprising the electron (e−) and electron neutrino (ν
e); the second is the muonic leptons, comprising the muon (μ−) and muon neutrino (ν
μ); and the third is the tauonic leptons, comprising the tau (τ−) and the tau neutrino (ν
τ). Electrons have the least mass of all the charged leptons. The heavier muons and taus will rapidly change into electrons through a process of particle decay: the transformation from a higher mass state to a lower mass state. Thus electrons are stable and the most common charged lepton in the universe, whereas muons and taus can only be produced in high energy collisions (such as those involving cosmic rays and those carried out in particle accelerators).
BOSON:
boson comprise one of two classes of elementary particles, the other being fermions. The name boson was coined by Paul Dirac[3] to commemorate the contribution of Satyendra Nath Bose[4][5] in developing, with Einstein, Bose–Einstein statistics—which theorizes the characteristics of elementary particles.[6][7] Examples of bosons include fundamental particles (i.e., Higgs boson, the four force-carrying gauge bosons of the Standard Model, and the still-theoretical graviton of quantum gravity); composite particles (i.e., mesons, stable nuclei of even mass number, e.g., deuterium, helium-4, lead-208[Note 1]); and quasiparticles (e.g. Cooper pairs).
An important characteristic of bosons is that there is no limit to the number that can occupy the same quantum state. This property is evidenced, among other areas, in helium-4 when it is cooled to become a superfluid.[8] In contrast, two fermions cannot occupy the same quantum space. Whereas fermions make up matter, bosons, which are "force carriers" function as the 'glue' that holds matter together.[9] There is a deep relationship between this property and integer spin (s = 0, 1, 2 etc.).
There are six types of leptons, known as flavours, forming three generations.[2] The first generation is the electronic leptons, comprising the electron (e−) and electron neutrino (ν
e); the second is the muonic leptons, comprising the muon (μ−) and muon neutrino (ν
μ); and the third is the tauonic leptons, comprising the tau (τ−) and the tau neutrino (ν
τ). Electrons have the least mass of all the charged leptons. The heavier muons and taus will rapidly change into electrons through a process of particle decay: the transformation from a higher mass state to a lower mass state. Thus electrons are stable and the most common charged lepton in the universe, whereas muons and taus can only be produced in high energy collisions (such as those involving cosmic rays and those carried out in particle accelerators).
BOSON:
boson comprise one of two classes of elementary particles, the other being fermions. The name boson was coined by Paul Dirac[3] to commemorate the contribution of Satyendra Nath Bose[4][5] in developing, with Einstein, Bose–Einstein statistics—which theorizes the characteristics of elementary particles.[6][7] Examples of bosons include fundamental particles (i.e., Higgs boson, the four force-carrying gauge bosons of the Standard Model, and the still-theoretical graviton of quantum gravity); composite particles (i.e., mesons, stable nuclei of even mass number, e.g., deuterium, helium-4, lead-208[Note 1]); and quasiparticles (e.g. Cooper pairs).
An important characteristic of bosons is that there is no limit to the number that can occupy the same quantum state. This property is evidenced, among other areas, in helium-4 when it is cooled to become a superfluid.[8] In contrast, two fermions cannot occupy the same quantum space. Whereas fermions make up matter, bosons, which are "force carriers" function as the 'glue' that holds matter together.[9] There is a deep relationship between this property and integer spin (s = 0, 1, 2 etc.).
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