Скалярлар мен фермиондар арасындағы Юкава өзара әрекеттесуі

Type of interaction between scalars and fermions
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

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 to model lepton masses.

A Yukawa coupling term to the Higgs field effecting spontaneous symmetry breaking in the Standard Model is responsible for fermion masses in a symmetric manner. Suppose that the potential has its minimum, not at but at some non zero value This can happen, for example, with a potential form such as In this case, the Lagrangian exhibits spontaneous symmetry breaking. This is because the non zero value of the field, when operating on the vacuum, has a non zero vacuum expectation value of

In the Standard Model, this non zero expectation is responsible for the fermion masses despite the chiral symmetry of the model apparently excluding them. To exhibit the mass term, the action can be re expressed in terms of the derived field where is constructed to be independent of position (a constant). This means that the Yukawa term includes a component

and, since both g and are constants, the term presents as a mass term for the fermion with equivalent mass This mechanism is the means by which spontaneous symmetry breaking gives mass to fermions. The scalar field is known as the Higgs field. The Yukawa coupling for any given fermion in the Standard Model is an input to the theory. The ultimate reason for these couplings is not known: it would be something that a better, deeper theory should explain.

A Yukawa coupling term to the Higgs field effecting spontaneous symmetry breaking in the Standard Model is responsible for fermion masses in a symmetric manner. Suppose that the potential has its minimum, not at but at some non zero value This can happen, for example, with a potential form such as In this case, the Lagrangian exhibits spontaneous symmetry breaking. This is because the non zero value of the field, when operating on the vacuum, has a non zero vacuum expectation value of

In the Standard Model, this non zero expectation is responsible for the fermion masses despite the chiral symmetry of the model apparently excluding them. To exhibit the mass term, the action can be re expressed in terms of the derived field where is constructed to be independent of position (a constant). This means that the Yukawa term includes a component

and, since both g and are constants, the term presents as a mass term for the fermion with equivalent mass This mechanism is the means by which spontaneous symmetry breaking gives mass to fermions. The scalar field is known as the Higgs field. The Yukawa coupling for any given fermion in the Standard Model is an input to the theory. The ultimate reason for these couplings is not known: it would be something that a better, deeper theory should explain.

It is also possible to have a Yukawa interaction between a scalar and a Majorana field. In fact, the Yukawa interaction involving a scalar and a Dirac spinor can be thought of as a Yukawa interaction involving a scalar with two Majorana spinors of the same mass. Broken out in terms of the two chiral Majorana spinors, one has

where g is a complex coupling constant, m is a complex number, and n is the number of dimensions, as above.