Up quark

The up quark is a particle described by the Standard Model theory of physics. It is a first-generation down quark- are the fundamental constituents of these nucleons. The proton contains two up quarks and a down quark, while the neutron contains one up quark and two down quarks.

The equivalence of mass and energy described in the theory of Special Relativity means that quickly moving particles have greater energy and so appear to have a greater mass at high speeds than while at rest.^[1] The strength of the strong forces holding the quarks in the nucleus suggests they are moving with relativistic speeds. Therefore, the majority of the mass in nucleons comes from the energy in the gluon field holding the quarks together, and not the quark masses themselves. The existence of up quarks was first postulated when Gell-Mann and Zweig developed the deep inelastic scattering experiments at SLAC in 1967.

Hadrons containing up quarks

Some of the hadrons containing up quarks include:

• Charged down quark, or vice versa.
• The neutral pion (π⁰) is a linear combination of up-antiup and down-antidown, as are the ρ and ω mesons.
• The η and η' flavorless mesons are linear combinations of several quark-antiquark pairs, including up-antiup.
• A large number of detected nucleons, the Δ baryons are made of only up and down quarks: the Δ⁺⁺ contains three up quarks, the Δ⁺ contains two, and the Δ⁰ contains only one.

See also

• Isospin

References