Technicolor: quark-like particles inside Higgs?

[rogerl]

Lee Smolin mentioned in "Trouble with Physics":

"The next-most-elegant hypothesis is that the Higgs boson is made up of a new kind of quark, different from those that make up protons and neutrons. Because this seemed at first a "technical" solution to the problem, these were called techniquarks. They are bound together by a new kind of force, similar to the strong nuclear force that bind quarks into protons and neutrons. Since the force in quantum chromodynamics is sometimes called "color", the new force is called, of course, Technicolor"

However when I read about Technicolor in Wikipedia, nowhere is it mentioned that Technicolor involves the Higgs boson made up of a new kind of quark or particle. Wikipedia said:

"Technicolor was proposed in the late 1980s by Kenneth Lane and Estia J. Eichten two Sakurai winning physicists currently working at Fermilab.[1] Instead of introducing elementary Higgs bosons, technicolor models hide electroweak symmetry and generate masses for the W and Z bosons through the dynamics of new gauge interactions. Although asymptotically free at very high energies, these interactions must become strong and confining (and hence unobservable) at lower energies that have been experimentally probed. This dynamical approach is natural and avoids the hierarchy problem of the Standard Model."

So is Technicolor about Higg bosons made up of more fundamental particles or is it unrelated to Higgs (if so, Lee Smolin is wrong?)?

 

[petergreat]

"Technicolor was proposed in the late 1980s by Kenneth Lane and Estia J. Eichten two Sakurai winning physicists currently working at Fermilab.[1] Instead of introducing elementary Higgs bosons, technicolor models hide electroweak symmetry and generate masses for the W and Z bosons through the dynamics of new gauge interactions. Although asymptotically free at very high energies, these interactions must become strong and confining (and hence unobservable) at lower energies that have been experimentally probed. This dynamical approach is natural and avoids the hierarchy problem of the Standard Model."

Not elementary, so composite, made of quark-like particles.

 

[daschaich]

I've fixed that first sentence you quote in the Wikipedia article, which was recently added and is flagrantly incorrect.

The difficulty here is (in my view) entirely related to terminology (in particular, the habit of using the name "Higgs" for anything with even the slightest relevance to electroweak symmetry breaking). Smolin and Wikipedia are saying pretty much the same thing, just with different terminology. (Though I don't trust Smolin's etymology -- I believe "technicolor" came first as a cute pun and brought "techniquarks" and techni-etc. along with it, after vanquishing the competing terminology of "hypercolor" that Eichten and Lane used. But this doesn't matter at all.)

Technicolor is a theory of electroweak symmetry breaking (the "Higgs mechanism", if you like). In its simplest forms, it introduce no new elementary scalar fields ("Higgs bosons", if you like). If you want to say that scalar technihadrons are "composite Higgses", you can do so -- but in my experience this might confuse non-expert audiences. If you want to say (as Sekhar Chivukula likes to put in his talks) that technicolor is "Higgsless since 1976!", you can do so -- but in my experience this might confuse non-expert audiences.

To get an idea of technicolor, the pions of chiral symmetry breaking in QCD are a better analogy than the elementary electroweak doublet (the "Higgs doublet", if you like) introduced in the standard model. Three massless technipions are eaten by the W and Z; any additional pseudoscalar technihadrons produced by the same chiral symmetry breaking process must have a large enough mass (more than roughly 125 GeV) to satisfy experimental bounds.

The conventional wisdom is that scalar technihadrons ("composite Higgses", if you like) would look a lot like the QCD sigma/f0(600) -- such a crap resonance that it wouldn't really make much sense to talk about it as a bona fide particle, "Higgs" or not. An interesting paper published earlier this year argued instead that relatively narrow scalars should be expected from modern (low-scale walking) technicolor models, with the lightest scalar "In several important respects... like a heavy Higgs boson with a small vev."

 

[zaybu]

I have often read that the Higgs bosons is responsible of giving mass to the particles. Asuming that technicolor would be the correct theory, would it also make that same claim?

 

[daschaich]

I have often read that the Higgs bosons is responsible of giving mass to the particles. Asuming that technicolor would be the correct theory, would it also make that same claim?

It depends what you mean by "Higgs", because this same name is commonly used to refer to many different (albeit interrelated) concepts. This is why I try not to use this terminology, and instead say what I mean.

Technicolor is a theory of electroweak symmetry breaking (the "Higgs mechanism", if you like). In its simplest forms, it introduce no new elementary scalar fields ("Higgs bosons", if you like). If you want to say that scalar technihadrons are "composite Higgses", you can do so -- but in my experience this might confuse non-expert audiences. If you want to say (as Sekhar Chivukula likes to put in his talks) that technicolor is "Higgsless since 1976!", you can do so -- but in my experience this might confuse non-expert audiences.

 

[arivero]

The point about being "higgsless" is really about the very badly misnomed "hierarchy problem", and perhaps colaterally the "fine tuning". Higgs mechanism as it is usually done needs to avoid further cuadratic divergences in the higgs field itself. This is the problem susy takes care of. So the real point is not if tecnicolor (and ETC and topcolor) is higgless, but if it suffers of some quadratic difergence in the same way that the elementary higgs.

 

[daschaich]

Well, I at least have some interest in electroweak-scale phenomenology itself, beyond the renormalization group structures of the various theories. Technicolor theories indeed have no fine-tuning or hierarchy problems like those of the standard model, but it's up to you how much you care about that.

Because I've been harping about terminology, I want to make it clear that neither of these problems are caused by the "Higgs mechanism" (electroweak symmetry breaking) itself. Rather, they are features of the "Higgs mechanism as it is usually done", commonly known as the standard model.

 

[arivero]

daschaich, it was not my intention to imply that I know other way to do the Higgs mechanism. Can you do electroweak symmetry breaking of a standard model unbroken Lagrangian into a non-invariant vacuum, without the higgs? And without any hierarchy problem too?

I am very surprised (see other thread) that the SM seems to have a hidden susy related to colour, and I have a hard time to understand why such susy is needed if there is no quadratic divergence at all.

 

[daschaich]

...Can you do electroweak symmetry breaking of a standard model unbroken Lagrangian into a non-invariant vacuum, without the higgs? And without any hierarchy problem too?

This all depends on what you mean by "Higgs":

Technicolor is a theory of electroweak symmetry breaking (the "Higgs mechanism", if you like). In its simplest forms, it introduce no new elementary scalar fields ("Higgs bosons", if you like).

Since there are no elementary scalars in typical technicolor models, there is no hierarchy problem, either: everything is asymptotically free. It's not exactly the standard model lagrangian (since it involves new nonabelian gauge interactions instead of an elementary scalar electroweak doublet), but it's still electroweak symmetry breaking.

I am very surprised (see other thread) that the SM seems to have a hidden susy related to colour, and I have a hard time to understand why such susy is needed if there is no quadratic divergence at all.

I will take a look at the other thread, which I have not yet seen. While supersymmetry can indeed cancel out divergent loops, this doesn't imply that divergent loops are required for supersymmetry to exist. More fundamentally it's the Coleman--Mandula theorem regarding conserved quantities in scattering processes that motivates supersymmetry; the cancellation is a pleasant phenomenological application of supersymmetry to stabilize the electroweak scale. Sorry if this is getting too tangential to this thread...