Yukawa

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 a scalar field (or pseudoscalar field) ϕ and a Dirac field ψ of the type





V
≈
g




ψ
¯




ϕ

ψ



{\displaystyle ~V\approx g\,{\bar {\psi }}\,\phi \,\psi \quad }
(scalar)






{\displaystyle \qquad }
or




g




ψ
¯




i


γ

5



ϕ

ψ



{\displaystyle \qquad g\,{\bar {\psi }}\,i\,\gamma ^{5}\,\phi \,\psi \quad }
(pseudoscalar).The Yukawa interaction was developed to model the strong force between hadrons. A Yukawa interaction is thus used to describe the nuclear force between nucleons mediated by pions (which are pseudoscalar mesons).
A Yukawa interaction is also used in the Standard Model to describe the coupling between the Higgs field and massless quark and lepton fields (i.e., the fundamental fermion particles). Through spontaneous symmetry breaking, these fermions acquire a mass proportional to the vacuum expectation value of the Higgs field. This Higgs-fermion coupling was first described by Steven Weinberg in 1967.

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