Can Supersymmetry be harmonized with technicolor/topcolor models?

[ensabah6]

Suppose the LHC discovers that EW is dynamically broken by technicolor, topcolor, top quark condensate models. Can these be harmonized with SUSY? If new strongly interacting dyanmics breaks EW, how would that modify SUSY, including SUSY particle content? Or, would discovery of technicolor/top quark condensate models rule out SUSY or make SUSY highly unfavorable?

 

[humanino]

They are not incompatible. The general idea was put forward by Witten ("Dynamical breaking of supersymmetry" Nucl.Phys.B188:513,1981 an "all time favorite" 1000+), one can find an explicit model in
Fermion Masses without Higgs: A Supersymmetric Technicolor Model

 

[ensabah6]

They are not incompatible. The general idea was put forward by Witten ("Dynamical breaking of supersymmetry" Nucl.Phys.B188:513,1981 an "all time favorite" 1000+), one can find an explicit model in
Fermion Masses without Higgs: A Supersymmetric Technicolor Model

thank you

 

[blechman]

from a "practical" point of view: susy was proposed to solve the "hierarchy problem" and "fine tuning problem" of the standard model. So was technicolor. Thus if one of these proposals is discovered, it would sort of take the wind out of the motivation for the other. that's why theorists typically don't combine them.

of course, that's no reason to close your mind to the possibility! and there are other justifications for new physics besides the hierarchy problem. but there it is, for what it's worth.

 

[ensabah6]

from a "practical" point of view: susy was proposed to solve the "hierarchy problem" and "fine tuning problem" of the standard model. So was technicolor. Thus if one of these proposals is discovered, it would sort of take the wind out of the motivation for the other. that's why theorists typically don't combine them.

of course, that's no reason to close your mind to the possibility! and there are other justifications for new physics besides the hierarchy problem. but there it is, for what it's worth.

Is there a reason the vast majority of physicist prefer Higgs + SUSY over dynamical technicolor models?

 

[humanino]

Is there a reason the vast majority of physicist prefer Higgs + SUSY over dynamical technicolor models?

The first "natural" technicolor models had been ruled out by precision electroweak models, so many people quit working on them. By now maybe a few dozens of people came up with various "improvements" (see extended technicolor or ETC, and walking technicolor) but one can argue that they are less "natural" and certainly more difficult.

Of course, the concept of "naturality" is dubious
I mention that after reading Naturally Speaking: The Naturalness Criterion and Physics at the LHC

 

[ensabah6]

The first "natural" technicolor models had been ruled out by precision electroweak models, so many people quit working on them. By now maybe a few dozens of people came up with various "improvements" (see extended technicolor or ETC, and walking technicolor) but one can argue that they are less "natural" and certainly more difficult.

Of course, the concept of "naturality" is dubious
I mention that after reading Naturally Speaking: The Naturalness Criterion and Physics at the LHC

Shouldn't the Tevatron have seen some of little higgs in MSSM ?

 

[humanino]

Shouldn't the Tevatron have seen some of little higgs in MSSM ?

I do not believe the Tevatron can constrain anything about Higgs even up to know :
Predictions for Higgs production at the Tevatron and the associated uncertainties
The uncertainties associated with the scale, in particular for gluon fusion, had not been taken into account properly.

This being said, little Higgs are pseudo-Goldstone and only require a broken global U(1). One does not necessarily investigate them specifically in terms of compositeness, as in technicolor models (that's my two-cents understanding).

 

[Haelfix]

In general a good phenomenologist can harmonize just about any of the conventional approaches into a single package, and sketch the backbone of the model rapidly (say 2 hours of work). Be sure that it has been done before many times and hep/ph is full of those papers. So supersymmetric warped extra dimensions, nmssm technicolor, etc etc

Sometimes it doesn't work, but there are so many knobs you can tune that you can often push things out of experimental detection range.

In fact its a little too easy, which is why people end up being skeptical of such Ruby Goldberg like constructions. Further they are often utilized to solve the same problems (eg the hierarchy problem, or the Mu problem, etc) so piling on extra stuff doesn't buy you anything other than to convolute the affair.

 

[ensabah6]

In general a good phenomenologist can harmonize just about any of the conventional approaches into a single package, and sketch the backbone of the model rapidly (say 2 hours of work). Be sure that it has been done before many times and hep/ph is full of those papers. So supersymmetric warped extra dimensions, nmssm technicolor, etc etc

Sometimes it doesn't work, but there are so many knobs you can tune that you can often push things out of experimental detection range.

In fact its a little too easy, which is why people end up being skeptical of such Ruby Goldberg like constructions. Further they are often utilized to solve the same problems (eg the hierarchy problem, or the Mu problem, etc) so piling on extra stuff doesn't buy you anything other than to convolute the affair.

understood. What about Top quark condensate?

 

[Haelfix]

I'm not sure what you are asking? Their potential relation to technicolor?

 

[ensabah6]

I'm not sure what you are asking? Their potential relation to technicolor?

The relation with technicolor, and if it is indeed the EW mechanism, whether it can also be reconciled with SUSY.

 

[Haelfix]

Try these papers, after a quick google scholar for "Top color assisted Technicolor".

C. T. Hill, Phys. Lett. B 345, 483 (1995);
K. Lane and E. Eichten, Phys. Lett. B 352, 383(1995);
K. Lane, Phys. Lett. B 433, 96 (1998);
G. Cvetic,Rev. Mod. Phys.bf 71, 513 (1999).
T. Rador, Phys. Rev. D 59, 095012 (1999);
C. Yue, et. al., Phys. Lett. B 536, 67 (2002);
C. Yue, et. al., J. Phys. G29, 737 (2003)

As for whether or not you can make that supersymmetric without hitting obstructions... I don't know. But if I had to guess, yea probably.

 

[ensabah6]

I guess to continue, what if LHC finds a single higgs and nothing else? or no higgs and nothing else?

i

 

[daschaich]

I'm sorry I wasn't around a couple of weeks ago for this interesting discussion. I'm writing my thesis on topics related to technicolor, so perhaps I can add something even after the fact.

First of all, on the subject of "supersymmetric technicolor", I would recommend those interested check out section 3.7 of the big technicolor review by Hill and Simmons, and the references therein. They begin with the Witten paper already mentioned by humanino, and also include at least one reference specifically on combining topcolor with susy.

Some brief comments on the previous discussions:

Is there a reason the vast majority of physicist prefer Higgs + SUSY over dynamical technicolor models?

What I consider the main reason doesn't seem to have been mentioned: technicolor is a strong interaction, analytically incalculable! If you want to perform some calculation in technicolor, you basically only have three options:

* try to extrapolate heuristic expectations from the single "data point" of QCD;
* try to develop some duality relating the model of interest to some weakly-coupled system in which calculations can actually be performed;
* try to use lattice gauge theory to construct improved heuristics or extract some nonperturbative inputs.

The first option isn't really reliable, and the others aren't really feasible yet, though a lot of effort is being put into them. I'm tempted to rant for a while, but I promised brief comments.

Of course, this isn't the only difficulty of technicolor models. Humanino mentioned that simple scaled-up QCD is experimentally ruled out (about which more below). And even without susy in the mix, ETC model-building quickly becomes very elaborate, with too many possibilities that can't yet be experimentally constrained.

The first "natural" technicolor models had been ruled out by precision electroweak models, so many people quit working on them. By now maybe a few dozens of people came up with various "improvements" (see extended technicolor or ETC, and walking technicolor) but one can argue that they are less "natural" and certainly more difficult.

ETC is not really an "improvement" of technicolor. Rather, it addresses a distinct issue from a similar perspective: While technicolor deals (only) with electroweak symmetry breaking (generating masses for the W and Z), ETC attempts to solve the "flavor problem" (generating fermion masses, mixings and CP violation).

The flavor problem is much more difficult than EWSB, and it pays to keep the two concepts distinct. My recollection is that one or the other (or maybe both) of these articles by Chris Quigg makes this point rather well:
http://arxiv.org/abs/0905.3187
http://arxiv.org/abs/0704.2232
It also comes up less explicitly in Ken Lane's "Two Lectures on Technicolor",
http://arxiv.org/abs/hep-ph/0202255

I would not describe walking theories as any more or less natural (or more or less difficult) than the earliest models of technicolor-as-scaled-up-QCD. Even though QCD is a confining theory, infrared fixed points are generic in gauge theories (cf. http://dx.doi.org/10.1016/0550-3213(82)90035-9 ), and it's reasonable to expect walking behavior around the strongly-coupled ends of "conformal windows". Of course, since these are strongly-interacting theories (as above), no one has yet rigorously demonstrated that walking can even occur, much less produce the desired effects.

Perhaps this is just a semantic issue depending on what we each mean by "natural".

from a "practical" point of view: susy was proposed to solve the "hierarchy problem" and "fine tuning problem" of the standard model. So was technicolor. Thus if one of these proposals is discovered, it would sort of take the wind out of the motivation for the other. that's why theorists typically don't combine them.

Personally, I find susy to be better motivated by the fact that it is the unique extension of Poincare invariance allowed by the Coleman--Mandula theorem. (I believe this is the historical motivation for susy as well, with applications to particle physics coming only after a few years of more abstract theoretical consideration.)

From a practical point of view, we would like susy and technicolor to "cure" each others' "problems". Sketchily, introducing susy-protected fundamental scalars (and their Yukawa couplings) could provide more leeway for ETC, making it easier to avoid experimental constraints from flavor-changing neutral currents. And on the other hand, if technicolor takes care of electroweak symmetry breaking, constraints on susy and susy-breaking phenomenology (which with I am less familiar) could also be relaxed.

This is also the general idea behind topcolor-assisted technicolor: topcolor takes care of part of the flavor problem (specifically, the large top quark mass) while (extended) technicolor deals with EWSB and less-problematic aspects of flavor. I'm told this hasn't really worked out, but I've never looked into topcolor much myself.

As Haelfix mentioned, the resulting constructions (like plain ETC models) are generally elaborate, Rube-Goldbergesque, and difficult to relate to experiment -- overall, probably not useful model-building exercises. But the general philosophy of "decoupling" the flavor problem from dynamical EWSB strikes me as a promising way to proceed. One interesting (if slightly tangential) approach to this that I read recently is the "monopole condensation" proposal by Csaki, Shirman and Terning: http://arxiv.org/abs/1003.1718

 

[blechman]

Personally, I find susy to be better motivated by the fact that it is the unique extension of Poincare invariance allowed by the Coleman--Mandula theorem. (I believe this is the historical motivation for susy as well, with applications to particle physics coming only after a few years of more abstract theoretical consideration.)

well, we all have our opinions. Personally (and this is just me, mind) this argument never did it for me. I mean, SUSY sidesteps the CM Theorem. So what?! I think the perturbative hierarchy solution is a much more significant reason to believe in it, if you do believe in it!

From a practical point of view, we would like susy and technicolor to "cure" each others' "problems". Sketchily, introducing susy-protected fundamental scalars (and their Yukawa couplings) could provide more leeway for ETC, making it easier to avoid experimental constraints from flavor-changing neutral currents. And on the other hand, if technicolor takes care of electroweak symmetry breaking, constraints on susy and susy-breaking phenomenology (which with I am less familiar) could also be relaxed.

a friend of mine wrote several papers (and effectively his PhD thesis) on models of SUSY in warped extra dimensions. I asked him, "Why are you doing both, if RS solves the hierarchy problem?" His answer: "RS solves the hierarchy problem, SUSY solves the RS-stabilization problem!" The moral of this story is: I think you are exactly right!

 

[arivero]

Is there a way to give the top a special role in susy (non technicolor, non top condensate) models? Because at the end, it is very peculiar: within 1-2%, all the other quarks and leptons have yukawa coupling =0, and the top has yukawa coupling =1.

EDIT: last year, dreaming about the D=11 SUGRA multiplet, the point that it has a field with 84 components (and not a field with 96 components anywere) seemed to me as an invitation to fit in there every the sfermions except the top. But never saw such a beast in a real model.