Quark

A quark ( /ˈkwɔrk/ or /ˈkwɑrk/) is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly observed or found in isolation; they can be found only within baryons or mesons. For this reason, much of what is known about quarks has been drawn from observations of the hadrons themselves.

There are six types of quarks, known as flavors: up, down, strange, charm, bottom, and top. Up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process of particle decay: the transformation from a higher mass state to a lower mass state. Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, top, and bottom quarks can only be produced in high energy collisions (such as those involving cosmic rays and in particle accelerators).

Quarks have various intrinsic properties, including electric charge, color charge, mass, and spin. Quarks are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as fundamental forces (electromagnetism, gravitation, strong interaction, and weak interaction), as well as the only known particles whose electric charges are not integer multiples of the elementary charge. For every quark flavor there is a corresponding type of antiparticle, known as an antiquark, that differs from the quark only in that some of its properties have equal magnitude but opposite sign.

The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964. Quarks were introduced as parts of an ordering scheme for hadrons, and there was little evidence for their physical existence until deep inelastic scattering experiments at the Stanford Linear Accelerator Center in 1968. All six flavors of quark have since been observed in accelerator experiments; the top quark, first observed at Fermilab in 1995, was the last to be discovered.

Read more about Quark:  Classification, History, Etymology, Interacting Quarks

Other articles related to "quark":

A Lord From Planet Earth - Technological Inventions - Quark Bomb
... The size of a soccer ball, the quark bomb is capable of destroying an entire planet, initiating subatomic fission ... There is no known defense from a quark bomb (see also Strangelet) ... The quark bomb explodes at the moment of construction at the factory ...
Stop Squark
... In particle physics, a stop squark is the superpartner of the top quark as predicted by supersymmetry ... While the top quark is the heaviest known quark, the stop squark is actually often the lightest squark in many supersymmetry models ...
Theta Meson
... a flavourless meson) formed by a top quark and top antiquark ... It is the equivalent of the phi (strange quark, strange antiquark), psi (charm quark, charm antiquark) and upsilon (bottom quark, bottom antiquark) mesons ... Due to the top quark's shortlifetime, the theta meson is not expected to be observed in nature ...
Cosmic Banditos
... Quark is a down-on-his-luck pot smuggler hiding out in the mountains of Colombia with his dog, High Pockets, and a small band of banditos led by the irascible ... Quark narrating one taking place in the present, high up in the mountains of Colombia and the other taking place in the past Mr ... Quark's adventurous account of pot-smuggling voyages on his ship, the Don Juan ...