jump to navigation

One more chunk of SUSY parameter space ticked off May 17, 2008

Posted by dorigo in cosmology, news, physics, science.
trackback

I am preparing the slides for the PPC08 conference, which will be held in Albuquerque next week, and I thought I would post here two slides that show how present Tevatron data is increasingly wiping off the board one Supersymmetric model after another – yes, I regard a choice of parameters as a single “model”, since the phenomenological implications of varying the >100 SUSY parameters are just too varied to call it a single model: instead, SUSY is a framework, and points in the parameter space are models.

The models we kill today belong to a version of the minimal supersymmetric extension of the Standard Model which has “minimal SO(10) soft-SUSY breaking boundary conditions“. No, I am not going to tell you what this is: you will have to read it on hep-ph/0506233 if you really must. Instead, I will show the present limit that CDF has obtained on a particular decay of the B_s meson, which is heavily suppressed in the standard model, but which could be enhanced by up to three orders of magnitude in SUSY models. Because of this enhancement, and because we could be sensitive to it, the matter is intriguing: by measuring the decay, one would instantly achieve two things: 1) prove the SM is wrong; 2) favor some SUSY models among the various possible interpretations of the effect.

B_s mesons are hadrons composed of a b and a s quark. They are electrically neutral, and have a long lifetime because the b-quark is unwilling to turn into a 2nd generation charm quark (decays across generations are suppressed). But they do, in about a picosecond. Blitzing fast for our senses, but quite slow for 5 GeV unstable subatomic bodies. What happens is that the b-quark emits a W boson, changing into the charm quark. The W boson is virtual, because it has a mass way below its nominal one of 80.4 GeV, and it immediately turns into a pair of light quarks or a lepton-neutrino pair.

What is described above is the rule, but there are exceptions. In an exceedingly rare combination of circumstances, the standard model predicts that a B_s meson will instead decay by emitting two W bosons, with a box diagram (see below, top) or a penguin diagram (bottom) whose end product may be a pair of charged muons: a striking signature of the decay! This, however, is calculated to happen only four times in a billion decays. That means we have to study several billion decays to observe it!

Searching in 2 inverse femtobarns of data, CDF has seen no signal, and a limit on the fraction of these rare decays has been set at 5.8E-8: no more than 58 in a billion. The search was done by looking for pairs of muons with an invariant mass compatible with that of the B_s meson, and by training a neural network on the dimuon kinematics and purity to distinguish true decays from other backgrounds.

In the slide below you can see the neural network discriminator output for signal and backgrounds, in the top right graph. The scatterplot in the lower right instead shows the NN output versus the reconstructed dimuon mass: the two small boxes are the regions where the signal for B_d and B_s mesons were sought.

The result on the branching fraction has implications on the models of SUSY with SO(10) soft susy breaking, as was said at the beginning. In the slide below you can see that indeed, for a particular choice of the parameters describing the space of these theories, the area not yet painted with any color – indicating it was still not disproven by searches of Higgs bosons, charginos, or other constraints – has been fully excluded by the CDF limit.

In the graph, the green band is the one most favoured by cosmological bounds on the relic density of dark matter. The full black line is the lower limit on charginos found by LEP. That bound has also been updated by CDF, and from 104 GeV the lower limit has been brought up to 140 GeV.

As Veltman puts it, “SUSY is hiding just around the corner… It has been hiding there for a while” (I am quoting by heart… but the meaning is unaltered). So, as we continue turning corners and finding nothing but good-old standard model physics, one starts to wonder whether we are fooling ourselves.

Comments

1. Guess Who - May 17, 2008

Methinks your Veltman source is DB:

https://dorigo.wordpress.com/2008/05/09/latest-lhc-schedule-and-luminosity-for-2008/#comment-97030

Veltman is quite a skeptic. This old (2001) lecture of his is fun if you can get it to load before the next millennium:

http://pauli.physics.lsa.umich.edu/w/arch/som/sto2001/Veltman/real/n001.htm

2. dorigo - May 17, 2008

Yes GW, I got aware of that sentence from that comment… The good sides of having a blog.

Cheers,
T.

3. Seth Zenz - May 17, 2008

Hi Doringo,

I’m curious about the idea of individual SUSY points as separate models. As you said:

I regard a choice of parameters as a single “model”, since the phenomenological implications of varying the >100 SUSY parameters are just too varied to call it a single model: instead, SUSY is a framework, and points in the parameter space are models.

Doesn’t that come close to implying that different values of the Standard Model parameters also constitute different models? I would propose that when a framework has a large space of possible parameters, it is the areas of parameter space with “qualitatively similar behavior” (however one defines that) which constitute a single model. Obviously there’s no rigorous way to define this, but it seems more sensible.

4. dorigo - May 17, 2008

Well Seth, yes – in a way that is what I would think it sensible to do.
There are parameters you can change which do not modify appreciably the phenomenology. But SUSY has just too many degrees of freedom. It is a framework, not a single theory. That is why these degrees of freedom are arbitrarily reduced to a smaller set, by making several assumptions: this allows to work with different models. mSUGRA is one – The one discussed above is another…

Cheers,
T.

5. Louise - May 17, 2008

“But SUSY has just too many degrees of freedom. It is a framework, not a single theory.”

This is great stuff. Supersymnetry in its best form just increases the number of free parameters. Many theorists have attached themselves to SUSY as if it were a person, while ignoring other theories. Like some other ideas out there, SUSY admits a divergence of solutions. This has kept SUSY theorists busy for years with their lack of success.

6. Evil String Theorist - May 18, 2008

Actually, TeV-scale supersymmetry makes some fairly generic predictions, namely a stable, electrically neutral particle and a light CP-even Higgs. For just the plain old MSSM with a top mass = 170.9 GeV, one can constrain the Higgs mass as 114 GeV < M_H < 120 GeV. The so-called free-parameters are just the supersymmetry breaking soft-terms which should be determined explicitly in whatever fundamental theory provides the UV completion of the MSSM, which is just a low-energy effective field theory. The assumptions made for a model of SUSY-breaking such as mSUGRA are quite reasonable and well-motivated, as one does expect universal soft-terms for gravity-mediated breaking to be universal.
It seems a little short-sighted to be opposed to something like the MSSM just because it has some free-parameters, which would be true for any effective field theory.

7. Mark - May 18, 2008

“The assumptions made for a model of SUSY-breaking such as mSUGRA are quite reasonable and well-motivated, as one does expect universal soft-terms for gravity-mediated breaking to be universal.”
I have to disagree with that because thare several compactification scenarious where, for instance, gaugino masses at the GUT scale are not universal because the gravity mediated contribution is suppressed relative to m_3/2 such that one gets anomaly or mirage mediation patters. Are these models ever used as benchmarks for SUSY? I’m not so sure…

8. forrest noble - May 18, 2008

It seems to me that Louise above has it right.

“SUSY has just too many degrees of freedom. It is a framework, not a single theory.”

As evidence comes in, interpretations can and have been rearranged in the SUSY framework. I have never seen a proposal mutually accepted on how SUSY might be disproved. Such a proposal is always a hallmark of a good theory.

Look at the BB theory as an example, no accepted proposal has ever been made how this theory might be disproved. At least SUSY makes predictions. BB theorists always assert predictions after observations. Internet search “unseen predictions of the BB” or similar wording. I never have found anything. Only those claiming a prediction after observations have been made. Hope we see none of that at CERN concerning SUSY };-> .

your friend forrest

9. island - May 18, 2008

T pulls no punches:
The models we kill today…

THIS is why I love you, man!…😉

10. Evil String Theorist - May 18, 2008

Dear Forrest,
The Big Bang Theory makes several predictions, which had they turned out to be wrong would, have falsified the theory. Namely, the fact that the universe is expanding (observed first by Hubble) and the cosmic background radiation (predicted by Gamow et. al. in 1948).

11. island - May 18, 2008

Conventional big bang theory is falsified by the horizon problem, the flatness problem, and the monopoles problem… if you disallow extraordinarily rapid inflation and other similar such nonsense that get made up in creation/evolution debate fashion to bend the rules…😉

Put it this way… if we don’t pre-assume a singularity, then when we project expansion backwards to the point where these issues arise, we don’t come to this conclusion.

Instead, we would most naturally conclude that the big bang occurred at the point where “re-thermalization” is understood to have taken place… in a universe with pre-existing finite volume.

There are no horizon, flatness, nor monopoles problems when there is pre-existing information projected into the initial conditions and the matter field… but “god” forbid that we question the unproven assumptions that include “adjusted physics” that make predictions after the observational fact.

12. forrest noble - May 18, 2008

Evil String Theorist,

Your right Evil, it made two predictions. The first concerning expansion was also predicted concurrently by the steady state theory via the continuous creation of matter explaining the apparent expansion. Many other theories have, I believe, equally explained the red-shift of galaxies and none of the more well know of these have ever been disproved.

My own finite-beginning diminution-of-matter theory (250 page long manuscript), and the related theory of matter relativity to time also readily explains the red-shift without resorting to either expansion or accelerated expansion. Simple math compared to Guth’s expansion theory. The second, the background radiation was long ago predicted by Eddington and scores of others up to the present time, as the radiation of matter heated by distant star light. No interaction between matter is required. Only absorption and re-radiation.

Since hydrogen in general occupies about one atom or proton per cubic meter of space it is the primary source of this evenly dispersed minuscule heat. About six months ago a radio astronomer in the U.S.claimed that intergalactic hydrogen radiates at the same background temperature as the observed MBR, and that our satellites could not distinguish the difference if there truly was CMBR. His finding were published in the prestigious Dec. 07, 07 Astrophysical Jounal. Some of the negative comments were: Was there a Big Bang, or simply a Big Bust of ill conceived Cosmology?

http://www.dsri.dk/~mykal/tmp/tycho/Verschuur.doc

I was an adult during the so-called background radiation prediction. I think you will find that it was just another case of hundreds of unknown predictions. It was, at the time, an obscure prediction of the countless hundreds or maybe thousands of alternative BB predictions. As you know a few researchers predicted 30 degrees Kelvin for a CMB.

I believe not only there prediction was not very close compared to Eddington’s, who was within less than one degree accuracy.

As I mentioned above, find a single current prediction of the BB. None are accepted by most BB theorists because their publication could undermine the theory. At least that’s my take on it. Also I suggest that only the understanding that there is no overall expansion, will the BB theory eventually fall. Granted if the CMB premise falls, the BB theory will be in more precarious waters.

Island, I also believe that true thinking is a premium in todays science theory.

your friend forrest

13. island - May 18, 2008

forrest noble said:
Island, I also believe that true thinking is a premium in todays science theory.

I think that this is probably only true because fundamental physics research is discouraged in order to concentrate on the ever increasing complexity that’s required to account for the previously mentioned assumptions.

But maybe you can appreciate something else that I feel complelled to say, from something that you said to Evil String Theorist.

forrest noble said:
The first concerning expansion was also predicted concurrently by the steady state theory via the continuous creation of matter explaining the apparent expansion.

But somewhere along the line somebody missed something relevant that nobody cares about now, because there is a whole bunch of support from the community for previously mention unproven assumptions, as well as their now-compounded extensions.

Depending upon the cosmological model that this takes place in, this continuing natural process necessarily increases tension between ordinary matter and the vacuum, which will inevitably compromise the forces that bind the structure, and we’ll have *another* big bang in a universe that has pre-existing finite volume, as described in my previous post.

What a coincidence:

http://www.lns.cornell.edu/spr/2006-02/msg0073320.html

14. Evil String Theorist - May 18, 2008

Dear Forrest,
First, the very idea of a continuous creation of matter as required in the steady state idea violates energy conservation, and from what basis do you explain how and why matter would be continuously created? In fact, where in the universe is this happening and why isn’t it observed? Secondly, even if this were happening, I fail to see how it would cause an expansion. Indeed, as the matter density increases the universe should simply collapse. Finally, what about Big Bang Nucleosynthesis (BBN) regarding the successful calculation of the relative abundances of hydrogen, helium, and lithium? How does the steady state theory explain this?

Island,
All of the issues explained by inflation were not things which falsified the Big Bang theory. The BB simply gave no answer for these questions by itself. On the other hand, inflation makes several testable predictions, some of which have been verified in recent years by WMAP and which will be further tested by Planck.

15. island - May 18, 2008

All of the issues explained by inflation were not things which falsified the Big Bang theory.

Uh… apparently you missed where I clearly pointed out why your statement is only true if we preassume a singularity under different conditions than we arrive at simply by projecting expansion backwards to the point where the horizon problem, DOES otherwise falsify ***conventional*** big bang theory.

And I say… bring on the experimients.

16. Evil String Theorist - May 18, 2008

Dear Island,
Neither the horizon problem, the flatness problem, nor the monopole problem falsify the Big Bang. These are just issues for which the theory does not offer an answer without fine-tuning. The idea of inflation solves these problems without fine-tuning.

Best,
EST

17. island - May 18, 2008

The idea of inflation solves these problems without fine-tuning.

LOL!

18. island - May 19, 2008

These are just issues for which the theory does not offer an answer without fine-tuning

Sorry, I probably shouldn’t have been openly disrespectful but my point is that there is a “singular” pre-assumption that inflationary theory is required to justify, which isn’t most naturally indicated by the reversal of expansion.

To say that it’s more plausible that we had some kind of extraordinarily rapid expansion event, rather than what it looks like, which is that we had a big bang at the point where the problems appear if you don’t preassum a singularity is laughable to me as long as I feel that there is a more clean solution, (that I illustrated and linked-to, for Forest, above).

The horizon problem and the background are accounted for when a causally connected universe of finite volume “rethermalizes”, so a viable mechanism for it that doesn’t even produce these “problems” is…. “cleaner”.

19. Evil String Theorist - May 19, 2008

Hi Island,
Your idea just sounds like more fine-tuning to me. The best suggestion I can offer you is to try to account for the relative abundances of hydrogen, helium, and lithium in your model. It seems to me that you would have a major problem accounting for the observed abundances.

20. island - May 19, 2008

Well, I don’t think so, and I’m not above being wrong, but it isn’t me who deserves a better look-see, and if “he” were here right now, you can bet he’d get it:

https://dorigo.wordpress.com/2007/10/18/

Sorry, T.

21. forrest noble - May 19, 2008

Hey Island, concerning no motivation to thinking:

“this is probably only true because fundamental physics research is discouraged in order to concentrate on the ever increasing complexity that’s required to account for the previously mentioned assumptions.”

Yeah, too bad. Sounds right to me, not that I can follow all those complexities anyway.

Evil,

The “continuous creation of matter (as) required in the steady state idea violates energy conservation, and from what basis do you explain how and why matter would be continuously created?

Certainly a good question since it was a question that also bothered me in the late 50’s when I first learned about it !! (I’m quite old) };-> .

Their answer was that matter was being created from the ZPF. That sounded like BS at the time to me, and it still does. Later, about 1960 Hoyle proposed an alternative: that the energy lost from fermion spin was recovered in the ZPF and reformulated into matter surrounding galactic size Black Holes. OK, that was a cool idea as far as I was concerned at the time, maybe not completely BS I thought.

My own theories now propose something similar to Hoyle/ Narlikar in 63. Both are diminution of matter theories. In my theory, about every half million years matter decreases about 10% in proportion to what it was before. Everything appears to be exactly the same except space would accordingly appear to be expanding at an accelerated rate, fancy that!!, even though there would be no real expansion at all, just an optical illusion of diminusion –

instead the lost material would be in the form of dark matter that reformulates around galactic Black Holes where forces create fermions from dark matter. If matter is being created from dark matter, there would be a time when there was just one beginning dark matter particle – at least that is the theory.

How about “the relative abundances of hydrogen, helium, and lithium in your model”, a question that must be addressed. …… I think BB theorists already knew the observed ratios before they started “calculating”. Maybe I’m wrong about this.

In my own theory (last copyright 1997, but published over and over again in my own mind) hydrogen and helium nuclei are created and fused from dark matter respectively, surrouding galactic Black Holes and jettisoned via their jets to form a surrounding galaxy. Additionally light elements are created by presently uncalculated (by me) fission processes within stars, do you think? =:-)X

Your friend forrest

22. DB - May 19, 2008

GW,

The source for Veltman’s comment was the 2001 lecture to which you linked.

Perhaps we should update his comment to take into account the time elapsed:)

It’s true he is a sceptic about a range of physical theories, but he is usually careful to differentiate between levels of scepticism. For example, he is extremely sceptical of string theory, pretty sceptical about SUSY, and mildly sceptical about the Higgs.

Physics appears to be losing its tolerance for scepticism, but the twentieth century – the second golden age of physics – was characterised by the most intense scepticism: within the mainstream Pauli, Feynman and Coleman make Veltman look like a pussycat, and outside the mainstream Einstein himself was no slouch when it came to criticising quantum theory.

So even when Veltman raises doubts about General Relativity, as he does, he is simply acting within a magnificent tradition.

23. Thomas Larsson - May 19, 2008

On the contrary, it seems to me that skepticism has made a major comeback during the past decade. That people care if some mathematician proclaims a non-theory to be magic or mystery, or that 400 people dance the macarena to celebrate some conjecture, were definitely anomalous events of the 1990s. Things like that are simply not happening today.

SUSY will of course not be discovered at the LHC. This is an immediate consequence of Larsson’s theorem.

“e non è colpa mia {…] se esiste l’imbecillità”

24. dorigo - May 19, 2008

Good grief, I leave this blog unattended for 22 hours of flights, and I find myself staring at 20 comments in this thread, many of which are above my head to effectively address.

So I’ll just nit-pick.

#6 EST: the current top mass is 172.6+-1.4, not 170.9. I admit it makes very little difference, but it does bring the allowed higgs mass range up a bit. About opposing SUSY: for me it is not just so much the fact it has what, 110 free parameters, 43 CP phases, etc…: it is just the fact that it appears to be constructed so that it is hiding where we havent found it yet. Big revolutions in physics happened by recognizing existing phenomena in a different context, rather than having to dig much deeper…
Island, Forrest, the current status of cosmology is not above well-motivated criticism: inflation and dark energy require faith to digest. However, I am with EST on this one: let’s see what Planck brings. In the meantime, dealing with dark matter appears a more intelligent option, since there we have lots of data to account for.

Thomas, I’m off to see your theorem (needed to finish this comment before leaving the page🙂

Thank you all for this interesting discussion, guys.
Cheers,
T.

25. My talk on new results from CDF « A Quantum Diaries Survivor - May 20, 2008

[…] suppressed in the standard model, which is enhanced in SUSY models. I discussed the latter result elsewhere […]

26. nc - May 21, 2008

On the reality of the big bang, can I recommend http://www.astro.ucla.edu/~wright/tiredlit.htm for an analysis of the redshift facts and the reasons why pseudoscientists can’t accept the big bang facts as valid.

Notice also that Alpher and Gamow predicted the cosmic background radiation in 1948 and it was discovered in 1965.

Actually, the big bang theory is incomplete, because when you take the derivative of the Hubble expansion law v = HR, you get acceleration a=dv/dt = d(H*R)/dt = (H*dR/dt) + (R*dH/dt) = H*v = R*H^2. This tells you that receding masses around us have a small outward acceleration, only on the order of 10^{-10} ms^{-2} for the most distant objects. This is a tremendous prediction. I published it via Electronics World back in Oct 96, well before Perlmutter confirmed it observationally.

This is just about the observed acceleration of the universe! Smolin points this amount of acceleration and the “numerical coincidence” that it is on the order of a = Hc = R*H^2 out in his book “The Trouble with Physics” (2006) but neglects to state that you get this result by differentiating the Hubble recession law! Note that arXiv.org allowed my paper upload from university in 2002, but then deleted in within seconds, unread!

Dr Bob Lambourne of the Open University years ago suggested submitting my paper to the Institute of Physics’ Classical and Quantum Gravity, the editor of which sent it for “peer-review” to a string theorist who rejected it because it added nothing to string theory!

So some additional evidence and confirmed predictions of the big bang do definitely exist (the outward acceleration of matter leads to radially outward force, which by newton’s 3rd law gives a predictable inward reaction force, which allows quantitative predictions of gravity that again are confirmed by empirical facts). Don’t just believe that only stuff that survives censorship by string theorists is factual. Classical and Quantum Gravity was publishing the Bogdanov’s string theory speculations (which the journal later had to retract) at the time it was rejecting my fact-based paper!

27. dorigo - May 22, 2008

Hi Nige,

it is unfortunate that good papers are rejected for silly reasons. But I guess in your case it will not stop it from appearing in print some way.

Are you willing to write a guest post on the prediction you made in 1996 ?

let me know.
Cheers,
T.

28. nc - May 23, 2008

Hi Tommaso, yes of course I would be delighted to. But I’m busy in my spare time at present writing a book which will be available free in PDF format on my domain when finished, and I really need to finish the book first, because doing so will force me to tie up a few outstanding loose ends. The one benefit to be censored out is that it gives me time to check out all of the implications in detail, instead of rushing to publish quickly.

29. Predictions for SUSY particle masses! « A Quantum Diaries Survivor - February 1, 2009

[…] For searches and their impact on SUSY parameter space, see here. […]


Sorry comments are closed for this entry

%d bloggers like this: