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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.
The second term is the CP violating θ-term, with the strong coupling constant, the gluon field strength tensor, and ~ the dual field strength tensor. The third term is known as the color anomaly , a consequence of the Peccei–Quinn symmetry being anomalous, with ξ {\displaystyle \xi } determined by the choice of PQ charges for the quarks.
The confinement scale or QCD scale is the scale at which the perturbatively defined strong coupling constant diverges. This is known as the Landau pole.The confinement scale definition and value therefore depend on the renormalization scheme used.
The strong force is the expression of the gluon interaction with other quark and gluon particles. 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.
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.
In particle physics, Yukawa's interaction or Yukawa coupling, named after Hideki Yukawa, is an interaction between particles according to the Yukawa potential. Specifically, it is between a scalar field (or pseudoscalar field) ϕ {\displaystyle \ \phi \ } and a Dirac field ψ {\displaystyle \ \psi \ } of the type
Examples of gluon coupling. Particles which interact with each other are said to be coupled. This interaction is caused by one of the fundamental forces, whose strengths are usually given by a dimensionless coupling constant. In quantum electrodynamics, this value is known as the fine-structure constant α, approximately
In quantum field theory and string theory, a coupling constant is a number that controls the strength of interactions in the theory. For example, the strength of gravity is described by a number called Newton's constant, which appears in Newton's law of gravity and also in the equations of Albert Einstein's general theory of relativity.