Breaking of isospin symmetry in theories with a dynamical Higgs mechanism
Abstract
The sensitivity of physical amplitudes to the observed isospinsymmetry breaking in the fermion mass matrix is analyzed in theories where the electroweak symmetry is dynamically broken. As a first step toward discussing dynamical theories in a modelindependent way, we consider a strongly interacting Higgs theory. The nonlinear σ model coupled to an SU(2)×U(1) YangMills theory and to fermions is used to generate the lowdimensional operators induced by the quantum theory. The strengths of these operators, in particular those that break isospin symmetry, are estimated using the Higgsboson mass of the linear σ model as a regulator. Technicolor models are next considered as a specific example of the stronginteraction physics which leads to electroweak symmetry breaking. Emphasis is placed on the effective fourfermion interactions that are natural partners of those which give mass to the ordinary fermions. New sources of isospinsymmetry breaking are found; in particular there is one which contributes directly to the ρ parameter with strength that is linear in the effective Yukawa coupling of the heaviest ordinary fermion. This effect is qualitatively different from the quadratic dependence found in Higgs theories.
 Publication:

Physical Review D
 Pub Date:
 April 1985
 DOI:
 10.1103/PhysRevD.31.1676
 Bibcode:
 1985PhRvD..31.1676A
 Keywords:

 11.15.Ex;
 11.30.Jw;
 12.10.Ck;
 Spontaneous breaking of gauge symmetries