Quarks
...terms, quarks are elementary fermions which engage in the strong interaction due to their color charge.[2] Because of a phenomenon known as color confinement, quarks are never found on their own in nature: they are always bound together in composite particles named hadrons.[3] The most common hadrons are the proton and the neutrons that compose atomic nuclei.
There are six different types of quarks, known as flavors: up (symbol: u), down (d), charm (c), strange (s), top (t), and bottom (b).[4] The lightest flavors, the up quark and the down quark, are generally stable and are very common in the universe, as they are found in protons and neutrons and are one of the primary building blocks of matter. The more massive charm, strange, top and bottom quarks are unstable and rapidly decay; these can only be produced under high energy conditions, such as in particle accelerators and in cosmic rays. For every quark flavor there is a corresponding antiparticle, or antiquark, that differs from the quark only in that some of its properties have the opposite sign.
The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964.[5] There was little evidence for the theory until 1968, when electronâ€"proton scattering experiments indicated the existence of substructure within the proton resembling three "sphere-like" regions.[6][7] By 1995, when the top quark was observed at Fermilab, all the six flavors had been observed.
Since quarks are not found in isolation, their properties can only be deduced from experiments on hadrons.[3] An exception to this is the top quark, which decays so rapidly that it does not hadronize at all, and instead is observed through the identification of the particles it has decayed into.[8] Furthermore, it has been theorized in some of the Big Bang theories, that in the very beginning, the extremely hot...
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