Yukawa

Hideki Yukawa (1907–1981) was a Japanese theoretical physicist who formulated the first quantum field theory of the nuclear force via meson exchange. He received the Nobel Prize in Physics in 1949 for his theory of the meson, the mediator of strong interactions.

In his meson theory, nucleons interact by exchanging a massive boson, which enforces a short-range force. Yukawa predicted a particle with a finite mass and a correspondingly short range, a prediction borne out experimentally with the discovery of the pion (pi-meson) in 1947.

The interaction is commonly described by the Yukawa potential, V(r) = -(g^2/4π) e^{-mr}/r, where m is the mass of the exchanged meson. This form explains why nuclear forces are short-ranged and how mass of the mediator sets the range ~ ħ/(mc).

In the Standard Model of particle physics, the term Yukawa coupling denotes the interaction between fermions and the Higgs field. After electroweak symmetry breaking, these couplings generate fermion masses; their strengths vary by fermion, with the top quark having a comparatively large Yukawa coupling.