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Hence, the actual value of the coupling constant is only defined at a given energy scale. In QCD, the Z boson mass scale is typically chosen, providing a value of the strong coupling constant of α s (M Z 2) = 0.1179 ± 0.0010. [7] In 2023 Atlas measured α s (M Z 2) = 0.1183 ± 0.0009 the most precise so far.
All quarks and gluons in QCD interact with each other through the strong force. The strength of interaction is parameterized by the strong coupling constant. This strength is modified by the gauge color charge of the particle, a group-theoretical property. The strong force acts between quarks.
The value of the fine-structure constant α is linked to the observed value of this coupling associated with the energy scale of the electron mass: the electron's mass gives a lower bound for this energy scale, because it (and the positron) is the lightest charged object whose quantum loops can contribute to the running.
The force between quarks is known as the colour force [6] (or color force [7]) or strong interaction, and is responsible for the nuclear force. Since the theory of electric charge is dubbed " electrodynamics ", the Greek word χρῶμα ( chrōma , "color") is applied to the theory of color charge, "chromodynamics".
(It is a non-trivial result of quantum field theory [2] that the exchange of even-spin bosons like the pion (spin 0, Yukawa force) or the graviton (spin 2, gravity) results in forces always attractive, while odd-spin bosons like the gluons (spin 1, strong interaction), the photon (spin 1, electromagnetic force) or the rho meson (spin 1, Yukawa ...
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured. Many of these are redundant, in the sense that they obey a known relationship with other physical ...
The strong coupling constant is conventionally labelled g s (or simply g where there is no ambiguity). The observations leading to the discovery of this part of the Standard Model are discussed in the article in quantum chromodynamics .
i is the imaginary unit; g s is the coupling constant of the strong force; t a = λ a /2 are the Gell-Mann matrices λ a divided by 2; a is a color index in the adjoint representation of SU(3) which take values 1, 2, ..., 8 for the eight generators of the group, namely the Gell-Mann matrices;