What Are the Key Features of the Simplest Higgs Model in Little Higgs Theory?

[whynothis]

Hello all I have a fairly specific question that I am hoping someone can answer. I have been doing some reading on a model called the Simplest Higgs (arXiv:hep-ph/0407143), one class of the more general Little Higgs theories.

Basically the model adds new physics to the standard model by extending the SU(2)xU(1) symmetry to SU(3)xU(1) and breaking it back down to the standard model using electroweak symmetry breaking generated by two scalar triplet fields. (If anyone has some familiarity with this models and sees something wrong with my interpretation of it comments would be appreciated)

While reading another paper (arXiv:hep-ph/0506313)discussing this model the authors make the following statement:

"...the simple group models share two features that distinguish them from
the product group models. First, the simple group models all contain an SU(N)×U(1)
gauge symmetry that is broken down to SU(2)L×U(1)Y , yielding a set of TeV-scale gauge
bosons. The two gauge couplings of the SU(N)×U(1) are fixed in terms of the two SM
SU(2)L×U(1)Y gauge couplings, leaving no free parameters in the gauge sector once the
symmetry-breaking scale is fixed. This gauge structure also forbids mixing between the
SM W± bosons and the TeV-scale gauge bosons..."

I don't understand why there can't be any mixing between the W's and the new bosons. Does anyone have any further insight on this?

I know this is a pretty specific question, any help or direction pointing would be a huge help. Thanks in advanced.

 

[BenTheMan]

I don't understand why there can't be any mixing between the W's and the new bosons. Does anyone have any further insight on this?

I think the answer is to look at the quantum numbers.

Only things that have the same quantum numbers can mix. Because the new gauge bosons must be neutral under the U(1)_Y (that is, they don't break that symmetry), they can't mix with things that ARE charged under U(1)_Y.

 

[whynothis]

I think the answer is to look at the quantum numbers.

Only things that have the same quantum numbers can mix. Because the new gauge bosons must be neutral under the U(1)_Y (that is, they don't break that symmetry), they can't mix with things that ARE charged under U(1)_Y.

Wonderful, thank you very much I will look into that.