The final panel discussion at the Maryland SEARCH workshop — six theoretical particle physicists talking about the 2011 experimental results from the Large Hadron Collider [LHC] and looking ahead to the 2012 data — has finally been posted online, along with the rest of the presentations at the workshop. I wrote about the workshop, which took place in mid-March, here and here. In the latter post, I wrote:
The workshop concluded with a panel discussion — the only point during the entire workshop when theorists were formally asked to say something. The panel consisted of Michael Peskin (senior statesman [and my Ph.D. advisor] famous for many reasons, including fundamental work on the implications of highly precise measurements ), Nima Arkani-Hamed (junior statesman, and famous for helping develop several revolutionary new ways of approaching the hierarchy problem), Riccardo Rattazzi (also famous for conceptual advances in dealing with the hierarchy problem), Gavin Salam (famous for his work advancing the applications of the theory of quarks and gluons, including revolutionary methods for dealing with jets), and myself (famous for talking too much… though come to think of it, that was true of the whole panel, except Gavin.) And Raman Sundrum, one of the organizers (and famous for his collaboration with Lisa Randall in introducing “warped” extra dimensions, and also anomaly-mediated supersymmetry breaking [which was competitive with a paper by Rattazzi and his colleagues]) informally participated too.
What I like most about this discussion is that it captures a historic moment, as we are still mulling over the field-altering implications of the 2011 LHC data, but before we have enough data to really figure out what it’s telling us. It is interesting to see where the panelists largely agree with one another and where they don’t. And it will be fascinating to look back at this video even as soon as a year from now; the same panel, if it were to be held in March 2013, would surely have very different things to say. Maybe when we get there I’ll ask the panelists to write about how their views have changed over the year.
I feel I should say something about the fact that all the members of this panel are male. You should not conclude that the leading figures in the field are all male. Certainly if Lisa Randall [Harvard University] or Ann Nelson [University of Washington], two of the greatest theoretical particle physicists working today (and with whom I was fortunate to write papers in the 90s), had attended this conference, I am sure they would have been sitting on this panel, in place of less eminent panelists (me, for instance).
Now on to the video:
Left to right (from the viewer’s point of view):
- Raman Sundrum [University of Maryland], (initially standing and speaking off camera),
- Michael Peskin [SLAC and Stanford University],
- Nima Arkani-Hamed [Institute for Advanced Study],
- Gavin Salam [CERN (the LHC lab), Paris and Princeton],
- Me [Rutgers University],
- Riccardo Rattazzi [Ecole Polytechnique Federale de Lausanne]
Questions are asked off-camera by professor Patrick Meade of the State University of New York at Stonybrook. (Meade, Sundrum and Michele Papucci of Berkeley organized the workshop.)
If you’re a particle physicist, you’ll have no trouble following the panel, but for those of you who aren’t, I’m afraid this is a high-level discussion which often lapses into jargon (see the limited glossary below). And it can get a little slow, so I think it unlikely that many non-experts will want to listen to the whole thing. So let me give you a few pointers (in both senses of the word).
- The discussion is 1 hour 23 minutes long.
- There are about two minutes of intro. Then from about 3:25 to 4:07 there’s a technical glitch which they didn’t edit out; skip til the video returns.
- From there, Professor Peskin presents his Four Slogans for 2012, which I described in an earlier post; now you can see them for yourself, though the language is quite technical.
Then the questions start (times listed):
- What would you personally most like the experimentalists at ATLAS and CMS [the two general-purpose experiments at the LHC] to look for in 2012? (0:09:00 – 0:30:00) [fairly technical answers]
- Do you think the excess seen at around a mass of 125 GeV/c2 in the search for the Standard Model Higgs particle is really a Higgs? (0:30:00 – 0:35:00) [less technical; this regards the hints in the data that I have written about here, here and here.]
- Where do you think supersymmetry stands right now, given that no sign of superpartner particles were seen in 2011, and given that there might be a Standard-Model-like Higgs at 125 GeV/c2?(0:35:00 – 1:05:00) [fairly technical; see the articles linked from this one for relevant background information, and this article for my detailed answer to this question.]
- What is the one experimental result that would give you the most insight into BSM (see glossary below) physics? (1:05:00-1:11:00) [fairly technical]
- What do you see as the role of theorists who think about BSM physics going into the coming year(s)? (1:14:00-end) [less technical]
At a minimum I recommend non-experts listen to a little of what the brilliant, entertaining, and famously long-winded Nima Arkani-Hamed, of the Institute for Advanced Study, has to say; he’s larger than life and a lot of fun to watch. He waxes poetic a few times, and in some cases reviews moments in scientific history in an interesting way; see examples at 0:14:45, 0:40:00 [over ten minutes!], 1:14:55.
If you are curious about my own views, I suggest 0:20:00 (Higgs and 2012), 0:32:00 (is there a Higgs particle appearing in current data?) and 1:20:00 (more general philosophy about doing physics at the LHC).
Finally, a short glossary to help the non-experts, and even the younger grad students, through the jargon.
- “QCD” = Quantum ChromoDynamics, the highly-developed theory of quark and gluons whose equations are crucial for predicting anything and everything at the LHC
- “BSM” = Beyond-the-Standard-Model (i.e. something from new particles and/or forces)
- “RS” = Randall-Sundrum version of extra-dimensions ideas.
- “hierarchy problem”; click here for an explanation.
- “theoretical prior” = strong expectation based on a combination of past experiments and the current theoretical framework of quantum field theory
- “SUSY” = supersymmetry
- “stop”= top squark, “sbottom” = bottom squark — superpartner particles of the top and bottom quarks
- “gluino” = superpartner particle of the gluon
- “flavor” = relating to the various types of quarks, charged leptons and neutrinos, mainly regarding their masses and their decay modes
- “WIMP” = Weakly-Interacting Massive Particle (i.e. a particle that feels the weak nuclear force) that might or might not make up the dark matter of the universe
- sequential z prime, – a heavy version of a Z particle
- vector like single top quark – a heavy version of a top quark, see http://profmattstrassler.com/2012/02/02/lhc-as-juggernaut-and-behemoth/
- TDR – technical design report for an experiment
- b tags – see http://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-apparently-elementary-particles/jets-the-manifestation-of-quarks-and-gluons/b-tagging-identifying-jets-from-bottom-quarks/
- Rpp decay = RPV decay = R-Parity-Violating decay = violation of assumption 1 in http://profmattstrassler.com/articles-and-posts/some-speculative-theoretical-ideas-for-the-lhc/supersymmetry/how-to-look-for-supersymmetry-at-the-lhc/
- maximally natural solution to heirachy problem = see http://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-hierarchy-problem/ first, then a natural solution is a theory that accomodates the hierarchy readily, for many possible values of its parameters, i.e. without the need to adjust the parameters of the theory to very precise values.
- long lived colour particles (color –> colored) = a heavy quark-like particle that lives much longer than a trillionth of a second and may travel some distance through (or all the way through) the ATLAS or CMS detectors before it decays
- relic abundance of DM = how much dark matter is left over after the Big Bang
- sigma term(time) branching ratio = sigma times branching ratio = production rate times the probability for a certain type of decay.
- natural theory at weak scale = see “natural solution to hierarchy problem” above; “weak scale” is around 1 TeV, meaning accessible to the LHC
- t/tbar/MET = top quark + top antiquark + missing tranverse momentum, as would arise from producing a top squark and antisquark pair, where the top squark decays to a top quark and an undetectable particle, and the top antisquark decays to a top antiquark and an undetectable particle
- sleuth type approaches = technique for simultaneously looking at all the data for deviations from predictions; sounds great but very dificult to carry out in practise
- top prime, bottom prime = heavy versions of a top quark and bottom quark
- natural v’s unnatural = the issue is whether a theory’s parameters must be precisely adjusted in order to get physics similar to our world (unnatural) or whether a wide range of parameters will typically lead to physics similar to our world (natural)
- 5/3 charge particles = just what it sounds like: particles with charge 5/3 times larger than that of a proton (compare with a top quark that has charge 2/3
- top squark = moderately likely (but by no means certain) to be the first superparticle discovered, IF supersymmetry exists of course!
62 Responses
Dear Prof Strassler re: the Higgs Boson
in Wikipedia, it says:
“The existence of the Higgs boson is predicted by the Standard Model to explain how spontaneous breaking of electroweak symmetry (the Higgs mechanism) takes place in nature, which in turn explains why other elementary particles have mass.”
I do not understand this sentence. I admit to not being knowledgeable about the Standard Model though I have read a bit about it. Can you tell me what spontaneous breaking of electroweak symmetry has to do with particles having mass. And why should the Higgs be probably on the order of 125 Gev, which is enormous? The graviton and photon which have unlimited range are supposed to be massless. Doesn’t the Higgs also have unlimited range? Also if the EMF is produced by an exchange of photons, how in the world do neutrinos of about 0.3 eV mass exchange 125 Gev particles. There I asked my big question. Thanks in advance for some sort of answer, even go read a particle physics book.
Yours, Sue Feingold
There are many reasons that this sentence in Wikipedia is confusing, if it isn’t properly explained. It’s almost useless if you are not an expert; it is way too short, jargony, and imprecise. I have several articles reaching over 2000 words on this very subject. Might I ask that you read them first?
In particular, you are confusing what the Higgs FIELD does with what the Higgs PARTICLE does, and that leads to most of your ensuing questions, which will be answered once you understand this point. In particular the Higgs particle is not responsible for giving other particles their masses; that’s the role of the Higgs field. And so its large mass (and the consequent short range of any effects of a force that it induces between other particles) has no bearing on the question of how other particles get their masses.
So — please read:
The Higgs FAQ
http://profmattstrassler.com/articles-and-posts/the-higgs-particle/360-2/
and some things about elementary particles
http://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-apparently-elementary-particles/
http://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-apparently-elementary-particles/the-known-particles-if-the-higgs-field-were-zero/
and then please come back and ask the questions that are bothering you at that point.
have you heard the feasibility of Bohr orbit quantization for multi-electron
Why would you want to do that? Multi-electron systems are beautifully described by the equations of quantum mechanics, which include Bohr orbit quantization as an approximation for hydrogen.
Hi All: Under Communism in Russia it was not permitted to contradict the pseudo science of Lysenko. And during the middle ages it was not permitted under the penalty to be burned, to question the Ptolemaic system. Prof. Strassler does not go that far in deleting my comments, when I answered his question if I had with my vacuum plasma model computed the electron neutrino mass, which I not only did, but published in 2000 to be about 0.05 eV. And he ignored my also at the same time given explanation of the parity violation by an imbalance in the vorticity acting on the W particle in the vacuum Planck mass plasma. And he ignored the fact that with the gravitational interaction of positive with negative masses one can get positive masses, eliminating the need for the Higgs. Therefore, ask him to let at least stay my comments long enough on his discussion page so that everybody can read them and can decide by himself if I am a fool or not.
Rant Rant Rant.
1) Mr. Winterberg: this is a free country, you can run your own website and put anything there you want. But this is a private website with a specific purpose; you do not have a God-given or legal right to write anything you like. And since you can’t take a hint to stop ranting, I have the right to ban you from this site until further notice. And that’s what I’m doing, as of this message.
2) Why are you banned? Because this is a serious website aimed at communicating established and ongoing science to the public. It is not a place for communicating highly speculative theories, not only ones that are obviously inconsistent with data such as yours, but even ones that don’t have obvious flaws. I will not permit this site to be cluttered with such things, whether good or bad. Do you see my string theory colleagues advertising their papers here? Do you see even my own personal theoretical ideas described on this website? Do you see long discussions of the latest investigations of the landscape of vacua that may or may not exist? No. Such ideas come and go; they don’t belong here.
3) The electron neutrino is not a mass eigenstate and does not have a mass. The general story is here
http://profmattstrassler.com/articles-and-posts/particle-physics-basics/neutrinos/neutrino-types-and-neutrino-oscillations/
And the most recent data is described here
http://profmattstrassler.com/2012/04/09/a-neutrino-success-story/
A theory that predicts that the electron neutrino is a state with a definite mass is inconsistent with data. Instead you must predict the masses and mixings of the three neutrino states; otherwise your theory makes no sense. The same is true of the quarks; if you predict the masses but not the mixings your theory makes no sense. So your prediction is wrong.
4) Your explanation of parity violation is inconsistent with data. If you put the parity violation in the helicity of the W particle instead of the chirality of the fermions, where it belongs, you will get answers that are inconsistent with data.
5) Your approach to predicting fermion masses is inconsistent with data until you fix (4).
6) Raise your standards. Go learn the Standard Model properly, at least as well as any first-year graduate student. And you need to learn the “equivalence theorem” and study both W pair production and top quark decay. When you can make intelligent statements about physics that are not obviously inconsistent with data, and when you’ve learned not to waste people’s time advertising your own personal research efforts before you’ve done your own homework to check that your results are consistent with data, you can be allowed back on this site. Until then, stop making comments; they will all be deleted — except this one, which remains as a matter of public record.
Dear Dilaton, Marcus Van Velzen, other Post Docs Grad-Students and gullible bloggers:You must understand that I am much smarter than Mr. Prof. Strassler. Here are the reasons why. I admit that he knows more than me about the detail of the SM, the MSSM et al., like a chemist knows the many chemical reactions but does not understand the Schroedinger equation which makes them possible. The SM and more so the MSSM et al., require at least 18 numbers (or 150) put in by hand. Do you believe nature is that complicated, or that our universe is one out of 10^500? Prof. Strassler is obviously afraid that I will win the debate (like Galileo once did) and rather than to face a good fight deletes my comments! This is not science but religous dogmatism he has accepted, very much as the enemies of Galieo who stuck to a 2000 year old wrong theory. The string theory people have adopted a wrong theory until now for (only) 40 years. I hope mankind does not have to wait for 2000 years to fund a theory which is “on the strings”. F. W.
Thank you for the entertainment Mr. Winterberg!! We have all had a good laugh at your expense.
I have deleted your comments (since you failed the test) but I still have them. I don’t want them here cluttering up serious scientific discussion, but if you insist, I’ll put them up again somewhere else. You made a great fool of yourself yesterday, and if you insist, I will make that extremely public and invite my colleagues in for a laugh.
Suppose for a moment that you are smarter than me — I’d be happy to concede the point. Very intelligent people can do very dumb things when they are ignorant of the facts. You’d better learn a bit more about the crucial details of the Standard Model before you attempt a new theory of nature; otherwise you’ll have a very nice but very wrong theory in the end.
Love Mr. Winterberg’s failure to answer a simple request for a calculation of his “results” — cuz, you know, that’s what real scientists do: make wild claims without any shred of proof — and then by completely changing the subject, giving first an ad hominem attack (how dare you criticize an 83 year old grandfather), and then by committing a blatant res herring fallacy (but I’m from a long lineage of distinguished physicists who studied under X, Y, and Z!) Bravo! Bravo!
It’s really a classic, isn’t it! 🙂
Huh, the last paragraph is interesting but I thought gravity can not be included in the SM using any real world methods so far …? Otherwise I would be very curious about how the inclusion of gravity can give mass to the neutrinos. I did not hear about this before …
You probably have heard this before: what I meant is this. The Standard Model without gravity is a renormalizable theory, so you would have only renormalizable terms in the Lagrangian of the theory. But the Standard Model with gravity is non-renormalizable, so one expects all higher-dimension operators suppressed by the Planck scale to appear in the Lagrangian, including (lepton doublet)(Higgs doublet)(Higgs doublet)(lepton doublet) = L H H L operators suppressed by one power of M_planck. After the Higgs gets an expectation value v, you expect neutrino masses of order v^2 / M_planck — much smaller than the top quark, whose mass is of order v itself.
Given how large the neutrino masses apparently are in nature, this estimate is actually too small.
But there is no surprise that the masses are non-zero; you would expect this. When I was a student in the late 80s, many theorists around me expected neutrino masses to be non-zero for precisely this reason. I mentioned this because Mr. Winterberg was making a big deal out of predicting neutrino masses wouldn’t be zero; well, so does the Standard Model in the realistic setting that you include gravity. If Mr. Winterberg had told me he’d predicted the right size for the neutrinos years before their rough size was measured, that might have made me a bit more interested.
Dear Prof. Strassler, thanks for this nice explanation.
And I enjoyed and admired how you resolved this issue with Mr. Winterberg, both thumbs up 😀
A problem with straight public rebuttal, different to private rejection, of a crackpot without reading nor discussing his work is that it can induce herding behaviour; ie more people that, being science gruppies and wanting to show themselves as scientists or future scientists, go to reject the work without understanding what is wrong inside.
On other hand, crackpot work has also different quality… The better ones go deep into the bibliography and sometime dig out old papers that were known (in folklore, at least) to our elders but that current research trends has left in the history dustbin. Of course they are ready to trash again such bibliography when pointed out that it doesn’t fit with the pet theory they really want to argue, but the process of data mining the history pile can get some pearls to interested students, helping to complete arguments, to know really why such or such topic was really discarded, or sometimes even to reuse them in a new context.
In this concrete case, I like that Winterberg has dug out some papers on a beloved topic of quantum mystics, Zitterwebewhatever, and its relation to composites. It seems that he wants to arrange fermions to be composites of a couple of peculiar bosons plus some ZitterMagic helping to set to h/2 the angular momentum of the total thing, and see this as a reinterpretation of Dirac equation.
Right. I have no objection to amateurs doing physics. My objection is to arrogance. How easily people convince themselves they are Einstein all over again, without understanding a thing about how careful Einstein was to make sure his theoretical advances were consistent with earlier data.
What is unfortunate about Winterberg’s approach is that matter is known (from data) not to obey the generalized Dirac equation but the generalized Weyl equation. The Dirac equation is parity preserving; nature is not. So the approach being taken cannot be repaired; because charged particles satisfying the Weyl equation are necessarily massless until symmetry breaking by the Higgs field. Take the Higgs field out, and no solution remains; you can’t have parity violation and fermion mass and the short-range weak nuclear force and the other features of nature that we’ve already observed. No serious scientist would claim to have made profound progress without dealing with this issue, which Winterberg either doesn’t understand or doesn’t think is important — both of which are damning.
He still has six hours to prove me wrong.
http://www.staff.science.uu.nl/~hooft101/theoristbad.html
I’m glad ‘t Hooft took the time to write this; and we can see that his previous attempts (duncan, take note) to make specific statements about specific people’s theories led to disaster (i.e. lawsuits). He’s absolutely right; he’s captured many of the obvious signs of an amateur in these paragraphs. I’d been thinking about writing a similar page (Advice for Amateurs) but for now I think I’ll just direct people to this one.
Mr. Winterberg, I hope you read this. You’re dangerously close to the edge here.
The most important thing about this page is actually not what it says about what amateurs do. It’s what is says about what professionals do. Professionals have far more humility than amateurs; we actually understand how hard it is to be Einstein. And this statement comes from ‘t Hooft, who really is a genius and among the best alive today; many of his papers in the 70s (at least 10 of them) changed the field.
Here is a funny appendix to Gerard`t Hooft s nice Sermon on the Mount to identify really bad crackpots … 🙂
http://math.ucr.edu/home/baez/crackpot.html
you say are deleting it as bad physics. I and assume others would learn more if you kept it as an example of bad physics and showed why point by point.
maybe even a section for bad physics,rebuttals.
Well, the problem is that I would waste huge amounts of time. Most of these people’s theories are obviously wrong, but typically the reason it is obvious to me is because of detailed technicalities that aren’t widely understood except by experts; they aren’t the things that are easy to explain. So if I’m to explain what is wrong with a given speculative theory, I typically have to do serious work to make sure I know exactly where the mistake is, and figure out how to explain it to a non-expert, which may not even be possible; after all, I’m a professional, so I’m not going to state where the mistake is until I know where it is precisely. Then, the moment I explain publicly where the mistake is, the author will either adjust the theory or tell me I’m completely wrong in a long series of irrelevant comments, just like the ones you’re seeing from Mr. Winterberg. He’s wasting my time and yours by not dealing with the issues that matter… he’s using the fact that current understanding of physics is incomplete to argue in favor of his own theory, instead of facing the fact that current understanding of physics is, in some areas, excellent, and his theory needs to be shown to agree with it before we waste our time on it. Can you imagine Einstein proposing a theory that didn’t obviously agree with both Newton and Maxwell? Well, that’s what this fellow is doing — proposing a theory that doesn’t in some obvious way preserve all the successes of the Standard Model. He hasn’t even bothered to check yet. If Einstein had walked in with general relativity without PROVING that it agreed with Newton’s theory of gravity, he would have been laughed off-stage. Mr. Winterberg doesn’t understand this. He should go off and work on it, and not start advertising it on other people’s websites until his homework is complete.
I recognise Gavin Salam on the panel from the series of short films Colliding Particles: http://www.collidingparticles.com/episode01.html This episode talks about their new method of discovering the Higgs that was published in a paper called: “Jet Substructure as a new Higgs search channel at the LHC”
A few years back — possibly around 2008 — Nima Arkani-Hamed gave a public talk suggesting it would take 3-4 years to confirm/rule-out the existence of the Higgs at 14Tev yet it now looks highly likely that this will be done within three years running at half the energy!
How did the theorists and experimentalists manage to do this?
woud you be able to comment on either of these 2 statements from his website
thanks
http://en.wikipedia.org/wiki/Friedwardt_Winterberg#cite_note-38
His current research is on the “Planck Aether Hypothesis”, “a novel theory that explains both quantum mechanics and the theory of relativity as asymptotic low energy approximations, and gives a spectrum of particles greatly resembling the standard model.
………
More recently, Winterberg has written an article stating that Einstein’s general theory of relativity cannot be reconciled with quantum theory in Einstein’s attempt to reduce all of physics to geometry.[39]
So far, I am extremely unimpressed with the quality of his discourse.
Matt, it’s estimated that we need around 15/fb of data this year for both Atlas and Cms to confirm/disprove the existence of a Higgs. If confirmed, will the 15/fb estimated this year plus 5/fb from last year be sufficient to tell whether it’s a susy or standard model Higgs?
No. The data MIGHT be sufficient to provoke strong suspicions that it is not a Standard Model Higgs. This is possible because the Standard Model makes very precise predictions for how a Standard Model Higgs will behave. But within supersymmetry, there is an enormous range of possibilities for how the Higgs will behave, including the possibility that it will behave rather like a Standard Model Higgs to a good approximation. This is true of other models as well.
Therefore it is almost impossible that the 2011-2012 data will show that the Higgs is inconsistent with supersymmetry.
It is also impossible that it will show that it is clearly consistent with supersymmetry and not with some other theory.
The only thing that is possible is that the 2011-2012 data will show the Higgs seems to be inconsistent with the Standard Model Higgs. It is unlikely (but possible) that this will be entirely convincing by the end of 2012.
The effort to determine the precise details of the Higgs may well take until 2020 or even later. That’s why the LHC was built to run for so long.
Hi Matt
I also watched this video with pleasure, even if I wasn’t able to understand it fully sometimes as it was a bit too technical, as Tim said above, it’s good to feel atmosphere. Part of discussion reminded me that I was going to ask you one thing. You and the other guys emphasised that all decay and production rates of Higgs must be carefully measured. It’s clear how can you measure decay rates, but how can you measure production rates? Meaning: you see Higgs particle in your data, naturally you see how it decayed, but how can you say which one of few possible ways it was produced? How this is done? I guess all Higgs particles look the same, no matter how they were created.
Thx, Pawel
No, actually there are several different mechanisms by which Higgs particles are produced, see http://profmattstrassler.com/articles-and-posts/the-higgs-particle/the-standard-model-higgs/production-of-the-standard-model-higgs-particle/
From that article, you can see that in different production modes, other things accompany the Higgs when it is produced: additional jets from quarks, a W particle, a Z particle, or a top quark/antiquark pair. So one can separate these different production modes by looking at what is produced in a collision along with a Higgs particle. It isn’t easy and needs a lot of data, but it will be done with reasonable precision (10%?) over the coming years.
I enjoyed watching the video ( at least the first 30 mins ) and soaking up the atmosphere. But there are so many term I don’t understand: sequential z prime, vector like single top quark, TDR, b tags, Rpp decay, maximally natural solution to heirachy problem, long lived colour particles, relic abundance of DM, sigma term(time) branching ratio, natural theory at weak scale, t/tbar/MET, sleuth type approaches, top prime, bottom prime, natural v’s unnatural, 5/3 charge particles . etc… etc…
Your short glossary helped a lot.
Is there a good reference place to understand in a non-technical way the meaing of many of these terms. Wikipedia helps a bit but tends to get too technical. ( maybe the answer is that I need to read everything you have blogged on this site 🙂 )
It seemed there was a fair amount of discussion around the stop particle. Is that seen as the most likely first superparticle that will be detected ?
sequential z prime, – a heavy version of a Z particle
vector like single top quark – a heavy version of a top quark, see http://profmattstrassler.com/2012/02/02/lhc-as-juggernaut-and-behemoth/
TDR – technical design report for an experiment
b tags – see http://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-apparently-elementary-particles/jets-the-manifestation-of-quarks-and-gluons/b-tagging-identifying-jets-from-bottom-quarks/
Rpp decay = RPV decay = R-Parity-Violating decay = violation of assumption 1 in http://profmattstrassler.com/articles-and-posts/some-speculative-theoretical-ideas-for-the-lhc/supersymmetry/how-to-look-for-supersymmetry-at-the-lhc/
maximally natural solution to heirachy problem = see http://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-hierarchy-problem/ first, then a natural solution is a theory that accomodates the hierarchy readily, for many possible values of its parameters, i.e. without the need to adjust the parameters of the theory to very precise values.
long lived colour particles (color –> colored) = a heavy quark-like particle that lives much longer than a trillionth of a second and may travel some distance through (or all the way through) the ATLAS or CMS detectors before it decays
relic abundance of DM = how much dark matter is left over after the Big Bang
sigma term(time) branching ratio = sigma times branching ratio = production rate times the probability for a certain type of decay.
natural theory at weak scale = see “natural solution to hierarchy problem” above; “weak scale” is around 1 TeV, meaning accessible to the LHC
t/tbar/MET = top quark + top antiquark + missing tranverse momentum, as would arise from producing a top squark and antisquark pair, where the top squark decays to a top quark and an undetectable particle, and the top antisquark decays to a top antiquark and an undetectable particle
sleuth type approaches = technique for simultaneously looking at all the data for deviations from predictions; sounds great but very dificult to carry out in practise
top prime, bottom prime = heavy versions of a top quark and bottom quark
natural v’s unnatural = the issue is whether a theory’s parameters must be precisely adjusted in order to get physics similar to our world (unnatural) or whether a wide range of parameters will typically lead to physics similar to our world (natural)
5/3 charge particles = just what it sounds like: particles with charge 5/3 times larger than that of a proton (compare with a top quark that has charge 2/3
top squark = moderately likely (but by no means certain) to be the first superparticle discovered, IF supersymmetry exists of course!
Thank you. I read through this and the referenced posts, then re-watched the panel discussion. I certainly got far more the second time through. You guys are in the process of making history.
So thanks for all questions you answer and for allowing the rest of us listen in whilst history is being made.
You are welcome. These are indeed extraordinary times.
Independently of the merits of the paper, I would like to promote this to a general question: Is there some model where a spin 2 graviton, either in 4, 10 or 11 dimensions, replaces the role of the Higgs? It is very amusing that both the D=11 SUGRA supermultplet and the MSSM bunch of particles are a 128+128. Besides, if we consider only the SSM, with massive W and Z (and wino and zino), the complection of multiplets tell us that it is a 126+126, the extant object could be either a graviton with its gravitino or the last piece of the higgs (two scalars and one higgsino).
No, there is no theory in which a spin-2 graviton replaces the Higgs. In four dimensions it couldn’t work; you’d have to go to higher dimensions, and use one part of the higher-dimensional graviton for your Higgs. But it would be very difficult; it wouldn’t be a simple replacement. You would need a much more elaborate theory to explain why the top quark ends up very massive and the electron ends up lightweight.
I don’t think you are going to get anywhere with the second part; it isn’t enough to count the particles, they also have to behave correctly. D=11 supergravity multiplets will not give a chiral field theory with diverse gauge group representations in four dimensions; the MSSM is chiral and has a complicated array of particles in various representations. And that’s probably the least of your worries.
Matt, what do you think of this paper
http://arxiv.org/pdf/0912.0208.pdf
These people predicted a Higgs boson mass of 125 Gev from asymptotic safety. If the evidence for 125Gev Higgs firms up, would you buy their models?
Thanks
No.
Look, 125 is a single number. One measly number. Dozens of people over the years have predicted a number for the Higgs mass. Some fraction of them, by pure statistics, are obviously going to include something near 125 within their prediction. And these people’s ideas contradict each other, so at most one (and possibly zero) of them are right.
Obviously we should not accept anyone’s idea just because it got this one number right. That would be not much better than giving an economist a Nobel Prize because s/he predicted the inflation rate in 2012 correctly; the criterion for a theory isn’t that it gets one thing right, it’s that it gets lots of things right.
Consider the electroweak theory. Combined with earlier experiments, it roughly predicted the W and Z particle masses — two measly numbers. But it predicted all the ratios of how often the Z and the W decay to the various different types of particles, and also angular distributions and asymmetries; it predicted how the top quark would decay, not only rates but also angular distributions; it predicted how bottom hadrons would decay and oscillate and so on. Based on dozens and dozens of measurements, the electroweak theory was accepted.
So no, I am not and never have been impressed by a theorist merely predicting the Higgs mass. Let’s see if (a) they get all the decay rates for the Higgs particle right, (b) they get all the production rates for the Higgs particle right, and (c) nothing shows up in the data that wasn’t predicted by their theoretical story.
Even after we’ve gone through this process and thrown away all the theories that are inconsistent with all the data, there may still be several contenders. Which one of these we should accept will not be obvious, in that case, and the answer will depend on the results of later experiments in future decades.
Expect this to take 20 years, 50 years, maybe 100. For the electroweak theory, the story started in the early 30s, with Fermi’s theory of the weak interactions; the last chapter began in the early 80s, with the discovery of the W and the Z, and came to a close with the detailed studies of the W, Z and top quark in the 90s.
If you want to get the right answer, and not be led down the wrong track, you have to be thorough, careful, and patient.
Hello Matt,
In general I agree with this reaction but could you please have a look at the article (if you haven’t already) and comment on it? I looked at it and although I do not understand it completely found it very convincing, at least worth considering. They pursue the asymptotic behavior of the renormalization group and looked for correct high energy behavior with the low energy behavior fixed by the low energy experimental values (top mass). In his talk at Cern (http://cdsweb.cern.ch/record/1188567) Weinberg said about this approach (asymptotic savety) that he wouldn’t bet his money on it (thinking the final theory would be something like a string theory) but it should be considered as a possiblity. The article concludes in january 2010 that “This results in mH = mmin = 126 GeV, with only a few GeV uncertainty”. Such a precise statement by serious physicists is quite remarkable.
Thanks for reply.
“Naively, the Higgs field should either be zero, or it should be as big as the Planck Energy …” Who are the world’s 10 best living theoretical physicists? I say that 5 of the 10 are Anderson, Weinberg, Glashow, Gell-Mann, and Witten. Why should Witten be on the list?
http://en.wikipedia.org/wiki/Edward_Witten
According to Witten, “Apart from gravity and gauge invariance, the most important general prediction of string theory is supersymmetry, a symmetry between bosons and fermions that string theory requires (at some energy scale). … Whereas in ordinary physics one talks about spacetime and ordinary fields it may contain, in string theory one talks about an auxiliary two-dimensional field theory that encodes the information.”
http://www.sns.ias.edu/~witten/papers/Reflections.pdf “Reflections On the Fate of Spacetime”, PHYSICS TODAY, 1996
I say 2 things: (1) A superstring is virtual mass-energy in a form that uses quantum information to unify spacetime and energy. (2) The fact that dark matter exists is strong empirical evidence in favor of supersymmetry, because supersymmetry in some form is the only mathematically plausible way to explain dark matter. Are (1) and (2) wrong? Does Higgs field imply that Seiberg-Witten supersymmetry exists, while no Higgs field implies that Fredkin-Wolfram supersymmetry exists?
No one is going to disagree with your list of leading scientists (though 5 out of 10? or 5 out of 20? we can debate.) Nor is your quote from Witten incorrect.
But I’m afraid your last two statements are wrong.
1) Your statement about what superstrings are is meaningless, and to the extent it has any meaning, quite wrong. Quantum information is not used to unify spacetime and energy; in fact, spacetime and energy are not unified in superstring theory, nor would it mean anything to unify them. What superstring theory does is far more subtle, and, arguably, not yet understood. At best what it does is offer the opportunity to unify the four known forces and the known particles in a single quantum mechanical setting.
2) Your statement about dark matter and supersymmetry is completely incorrect. There are many, many mathematically consistent ways to get dark matter. Nothing so complicated as supersymmetry is necessary. There are hundreds of papers in the literature about dark matter than do not involve supersymmetry. Moreover, it is possible that even with supersymmetry, dark matter has another source. Axions (a favored possible dark matter candidate) do not require supersymmetry. http://arxiv.org/abs/0904.3346 Extra dimensions can have dark matter candidates but no supersymmetry: http://conferences.fnal.gov/aspen05/talks/servant.pdf “Little Higgs” models can have dark matter: http://arxiv.org/abs/hep-ph/0603077 In fact, the problem with dark matter is that it is too easy to obtain. So no, the existence of dark matter is no evidence at all in favor of or against supersymmetry.
Finally, Seiberg-Witten supersymmetry does not exist; this is known. Supersymmetry was not invented by Seiberg and Witten; and the version of supersymmetry that Seiberg and Witten studied (which they also did not invent; they introduced a method for solving its equations) is mathematically very beautiful but is not appropriate for describing the real world. (Seiberg-Witten refers to the solution of N=2 supersymmetry, which cannot be chiral; but the real world, which is chiral, would be described by N=1 supersymmetry.) This is why realistic string theory compactifications involve something like a heterotic string on a Calabi-Yau manifold; that gets you N=1 supersymmetry. (You can find this in the famous and old Green, Schwarz and Witten textbook on string theory.) And that’s why all of Seiberg’s work on dynamical supersymmetry breaking is in N=1 supersymmetry. See for example this lecture by his collaborator Ken Intriligator (all of which involves N=1 supersymmetry, though he doesn’t state this explicitly since it is obvious to experts.) http://www.sns.ias.edu/pitp/2006files/Lecture%20notes/Intriligator%20lectures/Intril%20lecture%203.pdf
Whether there is or is not a Higgs field is independent of the question of whether there is or is not supersymmetry. We already know, from data, that there is a Higgs field (though there may be no Higgs particle.)
“… working with LHC data is extremely complicated and difficult, and the number of subtleties is enormous.” If the Higgs particle exists, then Brown totally does not understand physics. The way that I assess the Strassler versus Brown argument is this: The argument boils down to answering the question: Is Wolfram a serious rival to Newton and Einstein? If the answer is no, then Strassler wins and Brown is a crackpot. If the answer is yes, then Wolfram is as great as he thinks he is and both Fredkin and Brown look very good. Is this a fair assessment.
I enjoyed “Extra Dimension searches (monojet, monophoton, dilepton, diphoton) at CMS”.
It made me realize/appreciate the complicated work that goes into trying to compare a model with the data produced.
I think that it is probably harder to explain to an amateur.
Thanks
Oh, good. Yes, working with LHC data is extremely complicated and difficult, and the number of subtleties is enormous. The experimentalists deserve much more credit than they receive. I have enough trouble conveying this to my colleagues who are not LHC experts!
And this is one of the reasons I am more cautious about the current hints of a Higgs particle in ATLAS and CMS data than are many of my colleagues.
The language was not too technical. There were just too many words being said…. I get lost in the listening. I do much better when I am in the audience as an event participant, then I truly enjoy the rambling. Thank you for posting, though. Wish I was there!
Let me clarify my simple-mindedness. I am working on a children’s book on theoretical physics. I write so that children may understand without the obfuscation of academics and its hair spitting mathematical wooliness, or high-end technical considerations within the experimentation. I write so that children may simultaneously be spared the details while gaining a foothold in a field that has many misconceptions to the novice. I write so that children may have their curiosity kindled. I want children to feel comfortable while learning that there is plenty of spacetime remaining for their imagination to explore and understand correctly. Alas, as always is, there is so much more headroom for being wrong. My interests in theoretical physics goes back to the early days of string theory and M-branes in the 1970’s. To this day, I find that many of the ideas I am working on have already been explored by others (found in print) – except for a few ideas – which render me speechless. So I look to the visual arts to find like-minded souls. Children’s books need much illustration!
Simple-mindedness is fine; appealing to children is great. I am sure you will have a challenge ahead to find the right balance between making the book enjoyable, lucid and not too misleading; it is hard enough to find the right balance with adults. Good luck! Let me know when it is done.
OK, will do! I am aware of the challenge ahead of me. Simple is not easy. Language becomes like the shadows in Plato’s cave… but shadow puppets can be enlightening. It’s the differences in interpretation that become the source of enjoyment.
I just watched this this morning and found it really interesting.
One thing I was really surprised by is how you assess the odds of the Higgs signal being what it seems, and I think its fair to say you stood out as the real conservative on this question at 70% likely.
Im curious, what other scenarios occupy the biggest portions of that remaining 30%?
Cliff – you obviously didn’t listen carefully at all. What you said is completely wrong. Listen to Salam again. (He is the first panelist to say 70-30, not me!) And then reask your question; I won’t answer it in its current inaccurate form.
Cliff — since you haven’t yet apologized or revised your question, I will respond in my own way.
Salam and I both said 70-30; that’s one-third of the panel. From this you concluded “I think its fair to say you stood out as the real conservative on this question at 70% likely”. You have a bizarre notion of fairness to say that a person whose views are shared by 1/3 of a panel of 6 people “stood out”. Given the low statistics, for all you know my views are shared by 1/2 of the community. (1/3 among theorists is probably more accurate, based on my anecdotal conversations; experimentalists are much less confident.)
I would say that you stand out as having a viewpoint you’re trying to push so hard that you don’t actually listen to what people say. Did you hear what Arkani-Hamed said about the fact that if he didn’t have a strong theoretical prior, and only looked at the data, he would put the odds below 70-30?
So this is all about theoretical priors. Not about the evidence in the data, which several people in the panel agreed is weak.
I work much more closely with experimentalists (as does Salam) than do Sundrum or Arkani-Hamed or Rattazzi. Perhaps this explains some things. Why Peskin has such a strong thoretical prior I don’t know.
As for what I would put as the 30%, that refers to the possibility that (a) the excess in the current data is a combination of statistical fluctuations in the easier measurements combined with more subtle effects in the harder measurements, and (b) the Higgs particle (or particles) is (or are) a bit harder to find than expected in the Standard Model — for any of a dozen possible reasons, a few of which I described here:
http://profmattstrassler.com/articles-and-posts/the-higgs-particle/implications-of-higgs-searches-as-of-92011/
http://profmattstrassler.com/2012/01/27/exotic-decays-of-the-higgs-a-high-priority-for-2012/
Wow. Okay, so, Im sorry about the delay in responding, but I think its fair to say you dramatically interpreted the content of my question. I don’t see how its “unfair” to ask about your assessment, even if I was mistaken in the degree to which it stood out.
I just think 5 sigma is a reasonable standard for discovery, and we have two clear signals from the two experiments that you can add to somewhere around 4.5 sigma, so it seems to me to be a very strong conclusion that “it” is there. (Yes id realize sigmas are logarithmic.) And I realize that there are other important questions besides “there or not there”; will the branching ratios regress towards the SM expectations or not, is it an MSSM Higgs or some other SM extension, etc. Im not diminishing those questions at all but I think the odds are comfortably over 90% that this particle is the one corresponding to the potential that breaks electroweak symmetry, even if it might be different from the SM Higgs in some way.
I think its great that scientists have a bias towards being conservative in approaching their work but it doesn’t always translate to outsiders so well. All kinds of media accounts I read talk about “Will the Higgs finally come out of hiding this year?” As if when we finally get above 5-sigma level it will immediately go from “hiding” to being “caught”. I don’t think this is a rational way to way to communicate what goes on at the LHC. That is the real “garbage” as I see it, to borrow your terminology.
Yes, theoretical priors are relevant for this whole discussion. How could they not be? If the stuff we measure today was disconnected with everything else we’ve learned about physics there would be no point. Being skeptical of priors is prudent for experimental practice, but if we’re trying to honestly assess where we stand there should be no bias one way or anther without a rational basis.
I personally find it hard to believe that if you or Salam had to bet one way or the other whether the Higgs will be discovered around 125 GeV, with 90% odds in favor, that you would bet against it… But if you say so.
Well, you hit a nerve — saying that someone stands out when he doesn’t is not appropriate. I’m being accused of this over and over again by people who don’t actually talk to experimentalists; among experimentalists there is far more caution, and not because caution is prudent but because a lack of caution is imprudent.
Paragraph 2: “I just think 5 sigma is a reasonable standard for discovery, and we have two clear signals from the two experiments that you can add to somewhere around 4.5 sigma, so it seems to me to be a very strong conclusion that “it” is there”.
In saying this you assume there are no biases, no errors, no correlations among the experiments. History shows that many false results have occurred in the literature precisely because of these things. Does the word “Pentaquark” mean nothing to you? how about the discovery of the top quark in 1984? These things had large numbers of sigmas attached to them, but they were wrong anyway.
Also, you only get 4.5 sigma by combining everything together, which has many dangers; when you combine many unconvincing results together to make a convincing one, you run the risk that one error or large fluctuation can take down the entire argument.
Moreover, in obtaining this number you are assuming the Standard Model predictions for all production and decay rates are correct in nature, which they may not be! Most beyond-the-Standard-Model theories predict some of these rates will be changed. Assuming the Standard Model when you’re trying to test it is questionable methodology.
In summary, we agree that if you combine all the evidence naively you get 4.5 sigma. But these were not double-blind experiments, and the only thing you can learn from this naive combination is a naive conclusion.
As for “garbage”: I agree there is an issue of communicating with the public. The worst thing that could happen in public relations is that lots of scientists go around saying “we’re 95% certain we found the Higgs particle” and then it turns out that it’s not there. You saw the damage done by OPERA. There is good reason to be conservative.
I agree with you about theoretical priors; I’m not dismissing them. I’m just trying to separate them from the experimental evidence, which you call “4.5 sigma” and I call “naively 4.5 sigma”. (Notice that Arkani-Hamed agrees on this point: he specifically says that without his theoretical prior he’d put the odds from the data alone at below 70-30. Listen again; it’s after the first round of answers, when he follows up.)
But the point about theoretical priors is that intelligent people will have different ones. My theoretical prior is that we’re deeply confused about the hierarchy problem and there’s a good chance we’re facing a complicated Higgs sector which could be hard to find, so even though I too think the Standard Model is likely — enough to enhance weak evidence in data to 70-30ish odds — I weight the possibility that the Standard Model is wrong about the Higgs higher than some others do. That doesn’t make me right or wrong, it’s my personal feeling about the matter. My advisor Peskin feels very differently. That’s fine. We don’t have to argue about this; we’re no longer talking about what’s in the data, we’re talking about what the data makes us feel. It’s pointless to argue.
Your last point: I’m always amazed at how everyone talks about odds in this very silly way. If you bet me a dollar if the Higgs is there against 10 if it isn’t, I’ll take it. If you bet me a million dollars the Higgs is there against 10 million it isn’t, I won’t take it… because I can’t afford to lose. It’s not about the odds, it’s about the risks. So your remark is ill-posed.
One last remark: 70-30 is VERY HIGH ODDS. People forget this. If you asked me: do I think there is a Higgs (of non-Standard-Model type) at 137 GeV, or at 116 GeV, the answer is more like 5-95 or worse. Not 50-50. So you should be comparing 70-30 against things like 10-90 or 1-99 for any particular hypothesis. I think there is a very good chance that there is a Standard Model Higgs at 125 GeV, though I just don’t find the current experimental evidence convincing (because I think naive combinations are exactly that, naive); and I think there is a low chance of finding a non-Standard-Model-like Higgs at any other particular place, though integrated over all possibilities I still think there’s a moderate chance that the data is fooling us and the truth will lie elsewhere than 125 GeV.
Cliff, Prof Strassler considers all such scenarios to be rubbish…There s no point in trying to ask such questions here ;-).
Dilaton, please allow me to represent my own opinions; you can represent your own. It isn’t right for you to put words into my mouth.
Oh yep, I forgot that the original term you used in certain comments below a previous article was garbage.
I just wanted Cliff to stop asking such questionns here because they obviously annoy you … 🙂
He’s asking a different question; why do you conclude that it has the same answer?
And he’s trying to annoy me; fine, let me defend myself.
Because I`ve learned from recent descussions in the comments, that you probably consider the whole phenomenology business and any attempts trying to explain data observed at the LHC invoking some “deeper physical laws” (to put it mildly) as useless and therefore asking about or trying to discuss such things here is pointless. I`ll no longer do it, promised 🙂
For similar reasons, I`m now wondering why you explained and introduced concepts such as extradimensions and SUSY for example here on this site some time ago …
You say I “probably consider the whole phenomenology business and any attempts to explain data observed at the LHC invoking some `deeper physical laws’ as useless…”
WHAT?!
You have totally, utterly missed the point. I have no idea how you made such a staggering misinterpretation. Where the heck did you get THAT from?
Well, from some answers to Cliffs older posts a few days ago, from the answer to my question about the radion (yep, I`ve heard that the paper was wrong), and from an answer you gave to somebody aking what you really think about extra dimenstions, SUSY, etc …
Look, Dilaton, we barely have any data yet. We don’t even have confirmation that the Higgs is there at 125; even if you assume it is there, we don’t have any convincing information about what its production rates and decay rates are, so we have no idea yet whether we’re dealing with a Standard-Model-like Higgs or something else. It is far too early to draw conclusions. Yes, you see a lot of theorists writing papers about things in the data that will change by summer when new data comes in; fine, if that’s how they want to spend their time. When we get the 2012 data, that situation will improve dramatically. And I’m spending my time making sure we gather that data well.
As for SUSY and extra dimensions — we have no signs of any of those things as yet, but also the search strategies used so far are incomplete, so how can we draw any conclusions? If I tell you that I haven’t found my keys but I’ve only looked in four of the eight rooms, can I conclude whether or not my keys are in the house?
I’m not taking some principled stand that somehow we can’t draw important conclusions from LHC data. I’m saying that you can’t draw conclusions until you have sufficient data and you’ve done sufficient analysis. As for seeing phenomenology as “useless” — I do it for a living! It’s my job! And I fully intend to draw important conclusions from LHC data — when we have enough data and analysis to make such conclusions possible!