Non-standard gauge-boson self-interactions within a gauge invariant model

Abstract

We examine dimension-six extensions of the standard electroweak Lagrangian which are invariant under local SU(2) L × U(1) Y -transformations. The dimensionfour trilinear and quadrilinear effective interactions of the vector bosons with one another are found to coincide with the vector boson interactions previously derived from global SU(2) weak isospin symmetry broken by electromagnetism. Supplementing the model by a well-known dimension-six single-parameter quadrupole interaction leads to the most general vector boson self-couplings that can be obtained by addition of dimension-six terms to the standard Lagrangian. We examine in some detail another SU(2) L × U(1) Y -symmetric interaction which contains W 3 B mixing and modifies both vector boson self-couplings and fermionic interactions. Independently of being strongly constrained by the LEP 1 data, the addition of this interaction to the above-mentioned non-standard ones does not change the form of the trilinear and quadrilinear non-standard self-couplings of the vector bosons. Therefore, while being interesting in itself with respect to LEP 1 physics, this term is irrelevant with respect to the phenomenology of the vector-boson self-interactions.

On non-standard couplings among the electroweak vector bosons

“…The Lagrangian (3.16) contains three dimension-six and two dimension-eight terms. Restricting oneself to dimension-six terms [9,10,12] in (3.16) implies c 3 = c 5 = 0, (3.17) and thus the relations (3.10) and (3.12) [25] originally derived from symmetry arguments [1,2].…”

High-energy vector-boson scattering with nonstandard interactions and the role of a scalar sector

“…The phenomenologically relevant parts of the GINDIS Lagrangian in terms of the physical fields have been given in [22].…”

“…In this way one obtains an example of the second approach. The addition of a dimension-six single-parameter quadrupole interaction (which contains no scalar particles and is gauge invariant in itself) to this model leads to a general model for vector-boson self-interactions that can be obtained by adding gauge invariant dimension-six terms to the standard Lagrangian, provided some reasonable additional assumptions are made [22]. I call this model the GINDIS (gauge invariant dimension six) model.…”

“…Two other parameters,ĝ andg, describe the quadrilinear interactions. A two parameter reduction of the KMSS model, which I will henceforth simply call "the KMSS model", is obtained by imposing the conditions [22] g =ĝ 2 , g = 0.…”

“…A two-parameter reduction of the KMSS model can be embedded 2 [22] into a gauge-invariant framework. In this way one obtains an example of the second approach.…”