Up

Up Quark Stats

  • Symbol: u
  • Generation: First
  • Type: Up-Type
  • Antiparticle: Antiup
  • Mass: 1.8–3.0 MeV/c²
  • Charge: +2⁄3
  • Antiparticle Charge: -2⁄3
  • Colors: 3
  • Lifetime: Stable (or decays to d + e+)

The Up Quark

The up quark or u quark (symbol: u) is the lightest of all quarks and a major constituent of everyday matter. The up quark, along with the down quark, forms the everyday hadrons- neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark)-found in the atoms of ordinary matter.

The up quark is part of the first generation of matter, has an electric charge of +2⁄3 e and a bare mass of 1.8–3.0 MeV/c². Like all quarks, the up quark is a fundamental fermion with spin 1⁄2 and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions.

The antiparticle of the up quark is the up antiquark (sometimes called antiup quark or simply antiup), which differs from the up only in that some of its properties have equal magnitude but opposite sign.

History

The existence of the up quark— along with that of the down and strange quarks— was postulated in 1964 by Murray Gell-Mann and George Zweig to explain the Eightfold Way classification scheme of hadrons. The up quark was first observed in experiments at the Stanford Linear Accelerator Center in 1968.

Down

Down Quark Stats

  • Symbol: d
  • Generation: First
  • Type: Down-Type
  • Antiparticle: Antidown
  • Mass: 4.1–5.7 MeV/c²
  • Charge: -1⁄3
  • Antiparticle Charge: +1⁄3
  • Colors: 3
  • Lifetime: Stable (or decays to u + e- + ν̅e

The Down Quark

The down quark or d quark (symbol: d) is the second-lightest of all quarks and a major constituent of everyday matter. The down quark, along with the up quark, forms the everyday hadrons- neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark)-found in the atoms of ordinary matter.

The down quark is part of the first generation of matter, has an electric charge of -1⁄3 e and a bare mass of 4.1–5.7 MeV/c². Like all quarks, the down quark is a fundamental fermion with spin 1⁄2 and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions.

The antiparticle of the down quark is the down antiquark (sometimes called antidown quark or simply antidown), which differs from the down only in that some of its properties have equal magnitude but opposite sign.

History

The existence of the down quark— along with that of the up and strange quarks— was postulated in 1964 by Murray Gell-Mann and George Zweig to explain the Eightfold Way classification scheme of hadrons. The down quark was first observed in experiments at the Stanford Linear Accelerator Center in 1968.

Charm

Charm Quark Stats

  • Symbol: c
  • Generation: Second
  • Type: Up-Type
  • Antiparticle: Anticharm
  • Mass: 1290 MeV/c²
  • Charge: +2⁄3
  • Antiparticle Charge: -2⁄3
  • Colors: 3
  • Lifetime: Unstable, decays to s quark (~95%), d quark (~5%)

The Charm Quark

The charm quark or c quark (symbol: c) is the third most massive of all quarks. Charm quarks are found in hadrons that are not associated with the matter we experience in everyday life. Example of hadrons containing charm quarks include the J/ψ meson (J/ψ), D mesons (D), charmed Sigma baryons (Σc), and other charmed particles.

The charm quark is part of the second generation of matter, has an electric charge of +2⁄3 e and a bare mass of 1290 MeV/c². Like all quarks, the up quark is a fundamental fermion with spin 1⁄2 and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions.

The antiparticle of the up quark is the charm antiquark (sometimes called anticharm quark or simply anticharm), which differs from the charm only in that some of its properties have equal magnitude but opposite sign.

History

The 1974 discovery of the J/ψ (and thus the charm quark) ushered in a series of breakthroughs, which are collectively known as the November Revolution.

Strange

Strange Quark Stats

  • Symbol: s
  • Generation: Second
  • Type: Down-Type
  • Antiparticle: Antistrange
  • Mass: 95 MeV/c²
  • Charge: -1⁄3
  • Antiparticle Charge: +1⁄3
  • Colors: 3
  • Lifetime: Unstable, decays to u

The Strange Quark

The strange quark or s quark (symbol: s) is the third lightest of all quarks. Strange quarks are found in hadrons that are not associated with the matter we experience in everyday life. Example of hadrons containing strange quarks include kaons (K), strange D mesons (Ds), Sigma baryons (Σ), and other strange particles..

The strange quark is part of the second generation of matter, has an electric charge of -1⁄3 e and a bare mass of 95 MeV/c².Like all quarks, the up quark is a fundamental fermion with spin 1⁄2 and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions.

The antiparticle of the strange quark is the strange antiquark (sometimes called antistrange quark or simply antistrange), which differs from the strange only in that some of its properties have equal magnitude but opposite sign.

History

The first strange particle (a particle containing a strange quark) was discovered in 1947 (kaons), but the existence of the strange quark itself (and that of the up and down quarks) was only postulated in 1964 by Murray Gell-Mann and George Zweig to explain the Eightfold Way classification scheme of hadrons.

Top

Top Quark Stats

  • Symbol: t
  • Generation: Third
  • Type: Up-Type
  • Antiparticle: Antitop
  • Mass: 172900 MeV/c²
  • Charge: +2⁄3
  • Antiparticle Charge: -2⁄3
  • Colors: 3
  • Lifetime: Unsatble, decays to bottom quark (99.8%), strange quark (0.17%), down quark (0.007%)

The Top Quark

The top quark or t quark (symbol: t) is the most massive not only of all quarks, but of all observed fundamental particles. Because top quark is so massive, a large amount of energy is needed to create just one. The Standard Model predicts the top’s mean lifetime to be roughly 5×10-25 s. This is about 20 times shorter than the timescale for strong interactions, and therefore the top does not form hadrons, giving physicists a unique opportunity to study a "bare" quark (all other quarks hadronize, meaning they combine with other quarks to form hadrons, and can only be observed as such). The energy required to generate a top quark occurs naturally in the Earth's upper atmosphere where cosmic rays collide with particles in the air, but the only way to simulate this on Earth is in a large particle accelerator.

The top quark is part of the third generation of matter, has an electric charge of +2⁄3 e and a bare mass of 172900 MeV/c² which is about the same mass as an entire atom of tungsten. Like all quarks, the up quark is a fundamental fermion with spin 1⁄2 and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions.

The antiparticle of the top quark is the top antiquark (sometimes called antitop quark or simply antitop), which differs from the top only in that some of its properties have equal magnitude but opposite sign.

History

The top quark's existence, and that of the bottom quark, was postulated in 1973 by Makoto Kobayashi and Toshihide Maskawa to explain the observed CP violations in kaon decay, and was discovered in 1995 by the CDF and DØ experiments at Fermilab. Kobayashi and Maskawa won the 2008 Nobel Prize in Physics for the prediction of the top and bottom quark, which together form the third generation of quarks.

Bottom

Bottom Quark Stats

  • Symbol: b
  • Generation: Third
  • Type: Down-Type
  • Antiparticle: Antibottom
  • Mass: 4190 MeV/c²
  • Charge: -1⁄3
  • Antiparticle Charge: +1⁄3
  • Colors: 3
  • Lifetime: Unstable, decays to c or u

The Bottom Quark

The bottom quark or b quark (symbol: b), also known as the beauty quark, is the second most massive of all quarks. Bottom quarks are found in hadrons that are not associated with the matter we experience in everyday life. B Mesons are an example of a hadron containing a bottom quark. The bottom quark is also notable because it is a product in almost all top quark decays, and is a frequent decay product for the Higgs Boson.

The bottom quark is part of the first generation of matter, has an electric charge of -1⁄3 e and a bare mass of 4190 MeV/c², which is a little more than four times the mass of a proton. Like all quarks, the bottom quark is a fundamental fermion with spin 1⁄2 and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions.

The antiparticle of the bottom quark is the bottom antiquark (sometimes called antibottom quark or simply antibottom), which differs from the bottom only in that some of its properties have equal magnitude but opposite sign.

History

The bottom quark was theorized in 1973 by physicists Makoto Kobayashi and Toshihide Maskawa to explain CP violation. The name "bottom" was introduced in 1975 by Haim Harari. The bottom quark was discovered in 1977 by the Fermilab E288 experiment team led by Leon M. Lederman, when collisions produced bottomonium. Kobayashi and Maskawa won the 2008 Nobel Prize in Physics for their explanation of CP-violation. On its discovery, there were efforts to name the bottom quark "beauty", but "bottom" became the predominant usage.