The reality is that after 2/fb or so (pronounce: "two inverse femtobarns") that have been analyzed by each major detector of the LHC, no sign of new physics has been detected. It's still a beginning of the experiment and the total number of collisions inside the LHC will grow by orders of magnitude and the energy will be doubled, too. Each year of operation will have a comparable to chance to find something new as the first year. Or just a little bit smaller.
It's because the total amount of energy deposited in the final products of the LHC inelastic collisions is growing more or less exponentially and new physics has a pretty much uniform chance to emerge at the logarithmic energy scale.
It's the beginning but the LHC has already falsified many particular models with new phenomena predicted below 1 TeV or so - or, more precisely, with new phenomena visible in the first two inverse femtobarns. There have been lots of papers talking about possible observations in this region because many people liked things "behind the corner" that could have been a recipe for a quick journey to fame. It didn't work. ;-)
The experiments have surely not "punished" supersymmetry more than any other bottom-up theory even though many ignorant and deluded laymen such as Mr Ghosh are self-evidently obsessed with this utter misconception.
It's not even true that all superpartners with masses lighter than 1 TeV have been excluded. The firm exclusion only applies to superpartners that interact via the strong force - because it's easy to produce them by the "hadron" colliders such as the LHC. The other superpartners may be lighter and in fact, even many squarks may still be much lighter than 1 TeV. On the other hand, squarks may be much heavier and this actually allows the gluinos to be lighter than reported by the generic LHC data. Eminent SUSY phenomenologists Gordon Kane told the following to the SUSY-hating Marxist blogger Tommaso Dorigo:
I thought it was worthwhile to comment a little on recent LHC searches, since they have led to a number of surprising statements.Moreover, many of the search strategies depend on lots of events with large missing transverse energy - MET (i.e. particles that escape undetected through the detectors but that carry momentum and energy away - e.g. neutrinos or LSPs). In fact, the possibility that the new particles - whether they're superpartners or something else - manifest themselves by MET is arguably overstudied.
First consider gluino searches. The results of a search for gluinos are very sensitive to squark masses. Theoretically the only well motivated values for squark masses are very large, tens of TeV, because they are generically predicted in compactified string/M-theories when the associated moduli satisfy cosmological restrictions. Then
Existing gluino searches cover this region poorly. The current limit on gluino masses is not above 500 GeV. Whether the squarks are indeed so heavy is not the issue, the point is that if they are the limits on gluino masses are smaller than is often stated. I and others expect this decay to tops and bottoms is the signature by which gluinos will be found, with masses well below a TeV.
- (a) the gluino production rates are considerably reduced, and
- (b) the decays or gluinos to 3rd family final states dominate.
Second, when squarks are heavy the two doublet Higgs sector is an effective single doublet since the heavy partners decouple. There is a single light Higgs boson observable. If the gauge group of the theory is the MSSM one then the Higgs mass is between about 115 and 128 GeV (essentially a function of the parameter \(\tan\beta\)). It will not be above that range. It has the SM production rate. The LHC searches are not yet sensitive to this region, and should not yet have seen a signal, so not seeing a signal does not allow any meaningful conclusions about Standard Model or MSSM Higgs bosons.
Click here for a TRF blog entry fully dedicated to Gordon Kane's new scenario.
For example, Lisanti, Schuster, Strassler, and Toro recently proposed new strategies that focus on events with almost no missing transverse energy (or no MET at all) but with large multiplicities of particles - something that can result from complicated decay chains. Such things could even be natural and because these possibilities are understudied, the superpartners in this scenario could end up being much lighter than 1 TeV. (This particular paper is already obsolete a bit, because of the newest data, despite the paper's being so new, but its message that the experimenters haven't checked all qualitatively different possibilities holds.)
Lisa Randall's new book on particle physics and philosophy of science, Knocking on Heaven's Door, will be released on September 20th. Pre-order now.
More generally, there is nothing wrong with the Standard Model at 1 TeV - assuming that it contains something like the Higgs boson (which also remains undiscovered by the LHC but for certain reasons that are usually called "double standards", it wasn't "put on the spot" by the BBC). All imperfections of the Standard Model are of theoretical character and they only start to "scream" at mass scales much higher than 1 TeV.
The possibility that the LHC may discover nothing new besides the Standard Model (including one Higgs boson) is not a shocking new revelation: it's been discussed as one of the most likely scenarios for more than a decade. It has usually been presented as the ultimate nightmare scenario or as the death of particle physics.
I have always found such emotional descriptions loaded. The purpose of science is to understand how Nature works; the purpose of science is not to force Nature to behave in a way that brings financial advantages to some human beings who call themselves scientists. If there's nothing else than the Standard Model with a 119 GeV Higgs boson up to 5 TeV, well, then this is how Nature works. Nature has decided to promote people such as Glashow, Salam, Weinberg; Gross, Wilczek, Politzer; and others to the overlords of a pretty wide interval of energies. You may protest against this "injustice" but that's the only thing you can do against this fact - against this law of Nature.
Obviously, if the LHC ultimately happens to find strong evidence that there's nothing new and interesting to study below 5 TeV - and we're far from this conclusion at this moment - this insight will make it irrational to spend dozens of billions of dollars for a new lepton collider that could only reach similar energies. The rational - scientifically justifiable - decision will be to have the courage to do nothing, i.e. to build no new collider for quite some time. Of course, the funding for experimental particle physics should drop accordingly, including all the overheads and extra room that could feed many people linked to the particle physics community.
Some people are incapable of distinguishing the scientific truth, the scientific facts, and the rational decisions determined according to the scientific knowledge from their personal interests. It's just too bad if they can't distinguish those things. The fact that they would be richer if the Standard Model failed at 1 TeV doesn't mean that there is a scientific argument that it fails.
I personally don't find the "nightmare scenario" scary - I mean the hypothetical situation in which the Standard Model will be believed to be the only directly experimentally accessible theory in particle physics. If that's how Nature works, it's the duty for scientists to happily learn and accept this fact. Needless to say, the enigmas at the Planck scale, quantum gravity, and so on will continue to be vastly separated from the 1-TeV or 5-TeV energy scale. As long as people act rationally, the research of those serious matters should continue pretty much uninterrupted. For reasons that clearly follow from the comparison of energies, it's a mostly theoretical research; it's been like that for decades and only idiots such as Shmoits and their shameless readers have psychological problems with this inevitable fact.
But phenomenology of experimentally accessible phenomena in particle physics isn't over yet. I still find it very plausible - although never guaranteed - that there are new particles with masses between 100 GeV and 2 TeV or 5 TeV which will be found by the LHC. The LHC has just showed that it was irrational to expect dozens of new particles "right behind the corner". We should only expect roughly one or two new elementary particles every time we multiply our accessible energies by 10. There's just no reason why there should suddenly be an "avalanche" between 100 GeV and 1 TeV.
Back to phenomenology of 2011
So far, the LHC has only excluded models with new physics right behind the corner. Many of them were artificially "adjusted" to predict something new as soon as possible because that's what certain phenomenologists wanted. No doomsday for the Standard Model arrived but new physics may always emerge later.
The energy scale at which we may expect new physics has shifted to higher values. However, supersymmetry remains the single most justified class of models that may be expected to emerge at the LHC - or a more advanced collider in the future. Nothing has really changed about it.
Reviewing Mr Ghosh's article
I would like to discuss the article by Mr Ghosh and explain in some detail why I consider it an example of shoddy science journalism. First, the title:
LHC results put supersymmetry theory 'on the spot'This is a pretty hostile statement that is meant to make supersymmetry look bad - even though the LHC has so far rejected all sufficiently easily testable theories that predicted something else than the Standard Model phenomena. But fine. Someone may disagree with that. The title indicates that it's a quote.
When you read Mr Ghosh's article, you will find out that the quote comes from Dr Tara Shears of Liverpool who is, despite her female virtues, the "spokesman" of the LHCb collaboration. That's interesting that no one else than the politically correct BBC failed to adjust the gender properly in this case even though the masculine term "spokesman" is being carefully avoided when the spokesperson is actually male. ;-)
Dr Shears works for the LHCb and the recently infamous CDF Collaboration. It's great to be a "spokesman" but it's still true that she's not exactly a top physicist. With all my respect, titles in similar articles should depend on more important physicists. You can always find someone who says something you need for your piece with preconceived conclusions but it's just not an example of good journalism to pick anything just because it fits your agenda.
The first paragraph says:
Results from the Large Hadron Collider (LHC) have all but killed the simplest version of an enticing theory of sub-atomic physics.There is nothing such as "the simplest version" of supersymmetry that was killed. He probably means the MSSM but the experiments so far haven't really killed the MSSM yet. They have only killed some popular subsets of its parameter space - like "most" of the CMSSM or mSUGRA etc.
Researchers failed to find evidence of so-called "supersymmetric" particles, which many physicists had hoped would plug holes in the current theory.Incidentally, the Higgs sector looks more consistent with supersymmetry than with the "current theory" - the latter means the Standard Model. At any rate, the sentence above is misleading as well because it indicates that the Standard Model has "holes" at the scale accessible by the LHC now. It doesn't have any holes of this kind. It only has "holes" if you try to extrapolate it to much higher energies.
Theorists working in the field have told BBC News that they may have to come up with a completely new idea.This sentence is untrue for the same reason. The Standard Model works and it hasn't been refuted by the LHC so far. So this clearly means that physicists don't have to come up with any new ideas. There are no data that would require a new idea at this point. The sentence above is upside down.
Several paragraphs that follow inform that the LHCb has refuted another claim by the Tevatron - one about some rare decays of B-mesons. We should really discard all claims about new physics by the Tevatron.
Bitten the dust"Bitten the dust" is surely an eye-catching sequence of words. However, what should be more important, the proposition above is not correct. One can't say that one has excluded "the" simplest model of SUSY - which probably means MSSM. One has only eliminated low-energy corners of some popular constrained versions of MSSM.
This failure to find indirect evidence of supersymmetry, coupled with the fact that two of the collider's other main experiments have not yet detected supersymmetic particles, means that the simplest version of the theory has in effect bitten the dust.
Moreover, it's not really true that there are good reasons to think that supersymmetry, if realized in Nature, would be realized as the MSSM. Nature often avoids this naive kind of "minimality". I think it's more likely than not that even if SUSY is preserved up to low energies, the low-energy spectrum is something else than the MSSM.
A few paragraphs say that SUSY was developed 20 years ago. Well, SUSY was really born nearly 40 years ago and the MSSM was written down exactly 30 years ago. So all the numbers are wrong, but they're among the smaller problems of this shoddy article.
According to Professor Jordan Nash of Imperial College London, who is working on one of the LHC's experiments, researchers could have seen some evidence of supersymmetry by now.There hasn't been any derivation that would imply that the LHC has to find SUSY by now. But a more relevant comment for the journalist: it's just a flawed idea to ask experimenters - such as the CMS boss Mr Jordan Nash - about "our understanding". He doesn't seem to have too deep an understanding of the parameter spaces of supersymmetric theories. This is not a surprising criticism; he is an experimenter, after all.
"The fact that we haven't seen any evidence of it tells us that either our understanding of it is incomplete, or it's a little different to what we thought - or maybe it doesn't exist at all," he said.
He has tried to detect the evidence for particular models. But he has no capacity to distinguish which models were a priori "derivable" from some "understanding". Mr Ghosh shouldn't have asked experimenters about theoretical questions. But he apparently misunderstands the difference between theorists and experimenters.
There are two more catchy subtitles in the BBC piece - "disappointed" and "down the drain". ;-) The first one discusses a reasonable attitude of a nervous Joe Lykken who will attend the SUSY 2011 conference in Chicago: it starts tomorrow (on Sunday). Lykken is a good guy to talk about these issues and "disappointed" is an acceptable summary of his apparent feelings.
However, the next subtitle, "down the drain", is supported by nothing at all. Let me just go through this final portion of Mr Ghosh's article. The initial paragraphs of this segment of the BBC article suggest that more complex versions of SUSY have to be considered. It's not quite accurate but OK. A paragraph that follows says:
Some old ideas that emerged around the same time as supersymmetry are being resurrected now there is a prospect that supersymmetry may be on the wane.Oh my Ghosh. If supersymmetry were classified as "on the wane", technicolor would be doubly or triply "on the wane". It's kind of remarkable how the journalist only chose SUSY and fails to realize - in almost every sentence of his lousy article - that the LHC has excluded all other known kinds of new physics predicting new things in 2/fb, too. That includes light black holes, Randall-Sundrum gravitons, leptoquarks, preons, and lots of other things.
One has the whimsical name of "Technicolor".
For example, technicolor models such as Minimal Walking Technicolor predict new spin one particles. Those have been searched for by CMS and ATLAS, too. Heavy charged spin one bosons were excluded below 1.5 TeV. Those papers depended on the 36/pb collisions from 2010 only. I don't see substantially newer papers on the same issue yet. At this moment, the results show that the exclusion of technicolor models reaches even higher energies than supersymmetry - technicolor is more safely excluded by the LHC than supersymmetry so far.
(Obviously, it was always known that the upper bounds on SUSY would be the least constraining ones because SUSY is more "smoothly" compatible with the known physics than all other major models of physics beyond the Standard Model.)
So the idea that the data so far justify people's switching from supersymmetry to technicolor is unjustifiable. At least so far it is. Maybe the delay in the updated versions of the papers above suggests something? Stay tuned. ;-) Despite the floods of papers that say "nothing", there are many papers based on 2/fb or even 1/fb or so that haven't been published yet.
According to Dr Lykken, some younger theoretical physicists are beginning to develop completely novel ideas because they believe supersymmetry to be "old hat" .This is amusing, indeed. Why don't you ask Mother Nature to respect the quotas so that every generation - and every large enough nation and sex group - may reveal its own new and important discoveries? ;-)
"Young theorists especially would love to see supersymmetry go down the drain, because it means that the real thing is something they could invent - not something that was invented by the older generation," he said.
Needless to say, this reasoning is totally irrational. If someone pays a lot of attention to some generational (or national or sex-related) conflicts, he's simply not behaving as a scientist. Albert Einstein belonged to a very different generation than the people who are alive today. Does it mean that we should discount his discoveries? Is Nature obliged to offer us a new "theory of relativity" for us to feel "as successful as a previous generation"? Please, don't be silly. In various contexts, we're simply less successful. In some cases, it's even our fault.
Science evaluates theories by their internal strength and by their ability to explain as many empirical data as accurately as possible. Whether the originator of a theory is a conservative white male born in 1643 or a libertarian white male born in 1918 (I hope you can guess the names!) is simply irrelevant for the fate of scientific theories. Maybe Nature abhors the huge percentage of leftists in the current Academia so She won't give them any new and important secrets to be discovered - and She will give the last secrets to the last conservative white males on the periphery of the institutionalized science only. ;-)
The only relevant observation here is that none of the "young people" referred to in the paragraphs quoted above has found anything that would be as important as supersymmetry. A wishful thinking motivated by some crazy generational conflict - and justified by nearly zero of relevant scientific findings - simply shouldn't belong to a BBC article about science.
And the new generation has the backing of an old hand - Professor George Smoot, Nobel prizewinner for his work on the cosmic microwave background and one of the world's most respected physicists.There's always some backing by old guys. I actually think that the idea that the young people are mostly against SUSY disagrees with the real world sociological data. The most typical SUSY opponents are old and grumpy hippie as
Quite generally, bright phenomenology grad students and young postdocs typically love to work on SUSY even if their advisers do their best to redirect them to something else. I could tell you many examples but I don't want to include individuals into this discussion (some of the names have already appeared in this article, however). If they make new and radical progress in SUSY, then SUSY will also partly (or mostly?) belong to their generation.
My most well-known past contributions to science vitally depend on SUSY - even though it is in a non-phenomenological context (so all the discussions about the LHC observations are unrelated to it) - and so does a significant part of my ongoing unpublished research. For this reason, I consider myself to be a part of this research direction whether or not the majority of the leaders belong to another generation.
This scenario - that young people find something important about SUSY that will increase the ratio of stocks they possess in SUSY relatively to their older colleagues - is arguably more likely than the idea that they find something completely different than SUSY which is more important than SUSY. That's why sensible young particle phenomenologists learn SUSY and dedicate a significant part of their time to thinking about it - instead of pursuing scenarios in which they would maximally scr*w another generation if they happened to be successful (regardless of the odds that this may actually happen).
"Supersymmetry is an extremely beautiful model," he said.OK, so it's not supersymmetry. Fine: symmetry-super (or symmetry-cooper or Smoot-Cooper). Wow, what a diva. :-)
"It's got symmetry, it's super and it's been taught in Europe for decades as the correct model because it is so beautiful; but there's no experimental data to say that it is correct."
More seriously, George Smoot is clearly the main reference inside the part of the article titled "down the drain" which is crazy because even the very quotes above make it clear that he's a fan of SUSY. (Smoot also dedicated one full lecture in his courses in relativity to string theory.) The absence of a convincing and direct enough experimental proof at this point is an obvious fact that every sensible person must agree upon; the agreement with this fact doesn't make one an enemy of supersymmetry, and Smoot actually isn't one.
By the way, I also think that it's incorrect to say that SUSY is favored by Europe more than it is favored by America. SUSY has become one of the symbols of America, especially in the 1990s when its power (and I mean extended SUSY in this case) was unleashed by physicists such as Seiberg and Witten in Princeton, New Jersey. That was approximately the moment when Europe became the Second League of Supersymmetry. Even if you look at the phenomenology only, many of the leaders work in America - e.g. Gordon Kane, Joe Lykken, and lots of others I could enumerate.
Smoot's ideas about the "nationality" of SUSY are obsolete - which is not shocking because he's no historian of supersymmetry. Mr Ghosh should have rechecked this piece of information, too. Moreover, Mr Ghosh could have extracted lots of wisdom from George Smoot, too. Instead, he has only used Smoot's charming sense of humor in such a way that Smoot ultimately looks like a dumbass who has nothing substantial to say and who only serves as a complement to some less prominent scientists.
To summarize, Mr Ghosh should splash himself down the drain because his work is a pile of garbage.
BTW, Ghosh also recently wrote a report on the CLOUD experiment designed to test Svensmark's theory - the previous article on TRF - without mentioning Svensmark's name (not to mention other lethal problems with his text). My problems with certain journalists are usually very far from being one-dimensional ones. Some journalists are simply spherical bastards - they're bastards no matter what direction you observe them from.