Time for a Poll: Higgs Mass Prediction

[vanesch]

It is a bit stronger than that. It is the only way to enlarge the symmetry group of space-time. It is the natural extension of the Poincare symmetry, and there is definitely a prejudice that the laws of physics come from symmetries. So having space-time as symmetric as possible is definitely attractive. Even if you don't believe in low energy supersymmtry, it is very hard to live without high energy supersymmetry.

This is the kind of argumentation to which I'm rather insensitive. There are many possible symmetries in nature which simply do not turn out to be there, and there's no "principle of maximum symmetry" as far as I know. If it were the case, we wouldn't have CP violation, or even parity violation ; SU(5) would obviously be a better gauge theory than U(1) x SU(2) x SU(3)...
There are so many "missed occasions" in nature to have a certain symmetry that I don't think that it is justified, just because it is not impossible, to introduce a symmetry, just because it is a possibility. It's not excluded either of course and we should entertain the possibility of its existence.

I'm also not very sensitive to all those hierarchy and fine tuning "problems". To me, there is no qualitative difference between the real numbers between 1+10^(-20) and 1+10^(-15) on one hand, and 1.5 - 50.0 on the other hand. If it is a free parameter, it is a free parameter and it can just as well be part of the former interval as the latter. With a suitable mapping, we can get the former interval on the latter. It is IMO just psychological that we find the former "hard to believe" and the latter "normal free parameters".

That is not a fair criticism. Breaking supersymmetry is actually rather easy, so it is not an unreasonable thing to expect. The reason the models look a mess is simply because we don't know the mechanism of the breaking, so just parameterise it in a general way. Once the mechanism is known, the theory becomes quite predictive, with very few parameters.

Well, the day that there is a serious mechanism proposed, just a few parameters, and hard predictions, I might change my mind . But for the moment, the non-existence of a precise proposition of its mechanism of breaking allows one to introduce so many "free fit parameters" that one can morph it onto any set of experimental data.

Personally, I have the impression that the main success of supersymmetry is that it allows for easier computations in quantum models, because of the many cancellations that occur. Just make your theory supersymmetric, and you have better chances to have it computable. Whether that is a strong argument for a physical property, I don't know. Classically, integrable systems are also easier to consider. But most classical systems just aren't integrable.

Now, I'm taking some serious risks here, because I might have to eat my hat in a few years, when the LHC spits out superpartners with dozens. But for the moment, I don't bet on it.

EDIT: I must maybe soften my propositions a bit. It is probably because of ignorance that I don't see the compelling reason to almost assume supersymmetry as established, and just waiting for a kind of formal validation by experiment about which one hasn't much doubt. I simply haven't seen this reason yet, and maybe if I were to delve more deeply in its formalism, I might be convinced.

 

[arivero]

... the SM. Essentially, as soon as youy introduce new physics of any kind, the model becomes inconsistant. On its own it is fine, but we know it doesn't describe gravity and there is probably some new physics at some unification scale. Supersymmetry is not the only solution, but is probably the most elegant.

A N=8 gravity supermultiplet has 112+16=128=4*32 fermionic states. The Standard Model has 96+0=3*32 fermionic states. It seems to me that the Standard Model already has got to be at least a 75% of the final answer

More: considering that (112+16)-(96+0)=16+16, I'd say that the problem is to get rid of, or to explain or to predict, only 8 extra unwanted particles of spin 3/2. Of course, if you are in the orthodox way.

 

[Severian]

This is the kind of argumentation to which I'm rather insensitive. There are many possible symmetries in nature which simply do not turn out to be there, and there's no "principle of maximum symmetry" as far as I know. If it were the case, we wouldn't have CP violation, or even parity violation ; SU(5) would obviously be a better gauge theory than U(1) x SU(2) x SU(3)...
There are so many "missed occasions" in nature to have a certain symmetry that I don't think that it is justified, just because it is not impossible, to introduce a symmetry, just because it is a possibility. It's not excluded either of course and we should entertain the possibility of its existence.

The symmetries that you mention are all internal symmetries - not symmetries of space-time. Of course, no-one is saying that supersymmetry must exist just because it can, but it is a very attractive possibility, aesthetically speaking.

I'm also not very sensitive to all those hierarchy and fine tuning "problems". To me, there is no qualitative difference between the real numbers between 1+10^(-20) and 1+10^(-15) on one hand, and 1.5 - 50.0 on the other hand.

But that is not the problem. The problem is that the natural mass of the Higgs boson is the new physics scale, so if new physics appears at the Planck scale, the SM predicts the mass of the Higgs boson to be the Planck mass. But this is in contradiction with the requirement that the Higgs mass be less than about 700GeV to maintain unitarity. The issue is not that 10¹⁹ is a big number, it is that 10¹⁹ is a big number when compared to 700. No amount of (linear) remapping is going to change that.

It is IMO just psychological that we find the former "hard to believe" and the latter "normal free parameters".

No, it is a technically well defined problem. The phase space volume of allowed parameters is much much bigger than the phase space volume of allowed observables (before restricting the observables by measuements).

Well, the day that there is a serious mechanism proposed, just a few parameters, and hard predictions, I might change my mind . But for the moment, the non-existence of a precise proposition of its mechanism of breaking allows one to introduce so many "free fit parameters" that one can morph it onto any set of experimental data.

There are such mechanisms. For example, the constrained MSSM sets up the GUT values as would be compatible with supergravity models, and then has very few parameters, and makes hard predictions (which are getting close to being ruled out in fact).

Personally, I have the impression that the main success of supersymmetry is that it allows for easier computations in quantum models, because of the many cancellations that occur. Just make your theory supersymmetric, and you have better chances to have it computable.

That is not true. Supersymmetry does not make low energy phenomenological calculations easier (except one or two rather specific 'maximal helicity violating' multiloop processes). In fact it makes tham more difficlut because you have to calculate more diagrams. What it does do is make the results more palatable.

Of course, whether or not one likes SUSY is really an aesthetic choice, since there is no evidence for it yet. I happen to believe that the problems it solves are bigger problems than the problems it introduces, so aesthetically supersymmetric models are more pleasing. But it is equally valid to hold the contrary view.

 

[arivero]

The symmetries that you mention are all internal symmetries - not symmetries of space-time. Of course, no-one is saying that supersymmetry must exist just because it can, but it is a very attractive possibility, aesthetically speaking.

But the point was to bypass Coleman-Mandula. If we still have internal symmetries factores out, we have not bypassed the theorem.

 

[Haelfix]

I'm a big believer in GUTs (myriad reasons, including the favored explanation of a nonadhoc seesaw mechanism to set the neutrino masses to experimentally verified values, as well as leptogenesis concerns). Susy helps to make GUTs possible, ergo i'd be very surprised if we didn't see it at some scale. In a related way, its also one of the very few ways to evade Coleman-Mandula and solve the hierarchy problem. There just isn't very many other possibilities.

 

[vanesch]

But that is not the problem. The problem is that the natural mass of the Higgs boson is the new physics scale, so if new physics appears at the Planck scale, the SM predicts the mass of the Higgs boson to be the Planck mass.

This is what I don't understand. Given that the standard model doesn't deal with gravity at all, and given that it might probably need an entire paradigm change in order to include gravity, I don't see how the "planck scale" can pop out of the standard model or any other particle physics model given that it doesn't contain anything related to gravity. How does this "Planck mass" come into play here ? What's wrong with "new physics" at 20 TeV, say ?

 

[Kea]

On the other hand, it is true that something like the Higgs appears in Connes' NCG. Maybe this is what Kea has in his mind.

When Kea voted no Higgs, she was disagreeing with Connes, who is predicting a Higgs boson.

 

[Haelfix]

Err so how do you explain WW scattering? There aren't many alternatives to a higgs like mechanism, the only others I am aware off are riddled with phenomenological problems or are now safely ruled out.

 

[jgraber]

Whatever happened to the old GUTS?

I'm a big believer in GUTs (myriad reasons, including the favored explanation of a nonadhoc seesaw mechanism to set the neutrino masses to experimentally verified values, as well as leptogenesis concerns). Susy helps to make GUTs possible, ergo i'd be very surprised if we didn't see it at some scale. In a related way, its also one of the very few ways to evade Coleman-Mandula and solve the hierarchy problem. There just isn't very many other possibilities.

Since you're a big believer in GUTS, I will ask you a question I was thinking of making into a thread of its own:

Whatever happened to the old GUTS like SO(10), SU(4)xSU(4) and
Flipped SU(5)xU(1)?
As I remember it, these were the three leading contenders once SU(5) was ruled out. You never hear much about them these days. I understand that these GUTS can be included in the SO(32) and E(8)xE(8) that emerge from string theory and so subsumed as part of string theory. Still the bottom level or the level one up from the standard model seems important.
So I will ask a more detailed question related to the current thread:
Will the Higgs mass, or anything else we are likely to see at LHC, help us to distiguish between these three possibilities, or any newer ones?
Curious minds want to know.
TIA
Jim Graber

 

[CarlB]

This is the kind of argumentation to which I'm rather insensitive. There are many possible symmetries in nature which simply do not turn out to be there, and there's no "principle of maximum symmetry" as far as I know. ...

I love this post, (#31).

 

[arivero]

An argument FOR supersymmetry:

taking
d1^ , d2^ = neutrals
d+^ = charged +1, uncoloured
dr^, dg^, db^: colured, and charge -1/3we build:
1 fermion, |0>

6 bosons:
d1, d2, d+, dr, dg, db

15 fermions: as they appear in 5 and 10 of su(5) too
d1^d2, neutrino
d1^d+, positron
d1^dr, d1^dg, d1^db, three d-type quarks

d2^d+ the other degree of freedom of the positron
d2^dr, d2^dg, d2^db, the other three dof for the d-rype quark
d+^dr, d+^dg, d+^db three for the quark up
dr^dg, dr^db, dg^db three for anti-up.

20 bosons, a pretty mess:
d1^d2^d+, d1^d2^dr, d1^d2^dg, d1^d2^db
d1^d+^dr, d1^d+^dg, d1^d+^db
d1^dr^dg, d1^dr^db, d1^dg^db
d2^d+^dr, d2^d+^dg, d2^d+^d2^db
d2^dr^dg, d2^dr^db, d2^dg^db
d+^dr^dg, d+^dr^db, d+^dg^db
dr^dg^db

15 fermions, the oposite ones, in 10 + 5
d1^d2^d+^dr, d1^d2^d+^dg, d1^d2^d+^d2^db
d1^d2^dr^dg, d1^d2^dr^db, d1^d2^dg^db
d1^d+^dr^dg, d1^d+^dr^db, d1^d+^dg^db
d1^dr^dg^db
d2^d+^dr^dg, d2^d+^dr^db, d2^d+^dg^db
d2^dr^dg^db
d+^dr^dg^db

6 bosons
d1^d2^d+^dr^dg, ^d1^d2^d+^dr^db, ^d1^d2^d+^dg^db
d1^d2^dr^dg^db
d1^d+^dr^dg^db
d2^d+^dr^dg^db

1 fermion

d1^d2^d+^dr^dg^db

 

[humanino]

When Kea voted no Higgs, she was disagreeing with Connes, who is predicting a Higgs boson.

I am very sorry if I upset her. My appologies. Would she still please provide more details on her thoughts ? I know very little about NCG.

 

[Kea]

Would she still please provide more details on her thoughts?

The Higgs boson is introduced as an effective mass mechanism within the Standard Model. It cannot hope to explain mass generation within a theory of quantum gravity, which by definition must explain mass quantum numbers. So the question of its existence comes down to how far one is willing to extend the SM notion of Observable. What is a particle? Since our approach to QG (which has nothing to do with Connes' NCG) is not based on Symmetry, and since the effective QFT is not computationally gauge field theory, there is no reason whatsoever to think that the old idea of Observability should carry through to a scale where we fully expect New Physics.

 

[Severian]

It cannot hope to explain mass generation within a theory of quantum gravity, which by definition must explain mass quantum numbers.

Why not? The fundamental particles become massless above the electroweak symmetry breaking scale, so there is no mass to explain. You haven't explained why they have particular Yukawa couplings, but that is a different issue.

 

[arivero]

It sounds as the old issue of inertial versus gravitational mass.

 

[arivero]

An argument FOR supersymmetry:

Please refer to http://dftuz.unizar.es/~rivero/research/Newton.pdf for my current view of supersymmetry. Actually, my view three days ago . Page 1 is old stuff, page 2 is newer (to me).

 

[Kea]

Why not?

Quite simply because the Higgs mechanism is not used in the derivation of rest masses.

 

[humanino]

Please refer to http://dftuz.unizar.es/~rivero/research/Newton.pdf for my current view of supersymmetry. Actually, my view three days ago . Page 1 is old stuff, page 2 is newer (to me).

Ah, this clarifies your eariler post #41

I however still do not quite follow your arguments.
In particular, this hits me :

Having supersymmetry to composites helps to explain some features of charged leptons of the standard model. The pion mass if near of the muon mass. [...]

Do you have an explicit link between pion mass and muon mass !? They are not in the same generation (u and d quarks are in the first family, whereas the muon is in the second family), and even more intriguing, the mass of the pion arises from dynamical breaking of chiral symmetry, so if the muon mass is somehow linked to that, this seems big news to me. Are those only speculations ?

 

[arivero]

In particular, this hits me :Do you have an explicit link between pion mass and muon
mass !? They are not in the same generation (u and d quarks are in the first
family, whereas the muon is in the second family), and even more intriguing, the mass
of the pion arises from dynamical breaking of chiral symmetry, so if the muon mass is
somehow linked to that, this seems big news to me. Are those only speculations ?

what you read is what you get. Indeed, speculations. But note we need all the three generations to get the perfect pairing. So from the point of view of susy the pion is not a object exclusive of the first generation.

Page 2 is more orthodox but I have never seen the argument published neither.

 

[tehno]

No Higgs found (gut feelings).

 

[Severian]

Quite simply because the Higgs mechanism is not used in the derivation of rest masses.

Yes it is. Given the Yukawa couplings, you can predict the rest masses using the Higgs mechnism. (Of course, you have to input the Yukawa couplings, but as I said before, they are not masses, so they don't count.)

 

[Kea]

Yes it is.

I was referring to the rigorous derivation in the new approach to QG. Cheers.

 

[Severian]

I was referring to the rigorous derivation in the new approach to QG. Cheers.

I am sorry, but I am not sure what you are meaning? What does QG have to do with the Higgs mechanism?

 

[Kea]

What does QG have to do with the Higgs mechanism?

The fact that the QG derivation of particle masses (see Brannen) is carried out in a preon setting, free of any Higgs boson, which we conclude does not exist. I believe the existence of the Higgs boson is the topic of this thread, not the Higgs mechanism in the SM.

 

[Severian]

The fact that the QG derivation of particle masses (see Brannen) is carried out in a preon setting, free of any Higgs boson, which we conclude does not exist. I believe the existence of the Higgs boson is the topic of this thread, not the Higgs mechanism in the SM.

Sorry, I hadn't realized you were talking about BSM physics.

However, I am surprised that your preon setting is Higgs free. In the low energy effective theory where you integrate out the preon degrees of freedom (or rather the boson mediating the preon-preon interaction which holds them together inside the quark/lepton) I would still expect to have a condensate which couples to the fermions via a Yukawa coupling and gives it a mass.

In other words, the Higgs doesn't need to be fundamental to be a Higgs.

Of course, I am not familiar with your model, so it could be very different from what I am imagining.

 

[jgraber]

recently I found a link which reminded me that it is split supersymmetry which has a preference for a Higgs mass near 170 GeV. look at slides 6 and 7 in this reference.

http://james.physik.uni-freiburg.de/Graduiertenkolleg/talks/TPlehnFreiburg.pdf

So now I am puzzled why this option has not gotten more votes.
Best to all. Jim Graber

 

[Siul]

Hello,
Have you ever heard about Tony Smith's ideas in his extensive webpage ? What do you think about them ? Thanks !

 

[Severian]

recently I found a link which reminded me that it is split supersymmetry which has a preference for a Higgs mass near 170 GeV. look at slides 6 and 7 in this reference.

http://james.physik.uni-freiburg.de/Graduiertenkolleg/talks/TPlehnFreiburg.pdf

So now I am puzzled why this option has not gotten more votes.
Best to all. Jim Graber

Hmmm... why on Earth would Tilman be giving a talk on Split Susy. I know he thinks its crap. (I will have to tease him about it :D)

 

[Euclidistheway]

A MSSM Higgs

My bet is the detection of a MSSM light Higgs at 114.5635 GeV. This is dependent on the top quark mass 170.9666 GeV. This lower and upper bound is from the dynamics of two Nambu-Goldstone bosons generating 248 gauge fields (1/2 of the NG superfield). A strong colour mixing of the 124 gauge fields of the single NG boson generates the lower bound while the 248 gauge fields of the two NG bosons strong colour mix to generate the upper bound. This prediction is the precise result of the fermion superstring action on the CFT going massless and bosonic as the potential is pushed. The light Higgs signal is the result of the theory in ½ of the SUSY potential therefore the LHC results will not distinguish between the MSSM and the SM validity on the basis of this specific.