A commenter on the previous posting has helpfully given us the abstract of an internal ATLAS note claiming observation of a resonance at 115 GeV. It’s the sort of thing you would expect to see if there were a Higgs at that mass, but the number of events seen is about 30 times more than the standard model would predict. Best guess seems to be that this is either a hoax, or something that will disappear on further analysis. But, since spreading well-sourced rumors is more or less in the mission statement of this blog, I think I’ll promote this to its own posting. Here it is:
Internal Note
Report number ATL-COM-PHYS-2011-415
Title Observation of a γγ resonance at a mass in the vicinity of 115 GeV/c2 at ATLAS and its Higgs interpretation
Author(s) Fang, Y (-) ; Flores Castillo, L R (-) ; Wang, H (-) ; Wu, S L (University of Wisconsin-Madison)
Imprint 21 Apr 2011. – mult. p.
Subject category Detectors and Experimental Techniques
Accelerator/Facility, Experiment CERN LHC ; ATLAS
Free keywords Diphoton ; Resonance ; EWEAK ; HIGGS ; SUSY ; EXOTICS ; EGAMMA
Abstract Motivated by the result of the Higgs boson candidates at LEP with a mass of about 115~GeV/c2, the observation given in ATLAS note ATL-COM-PHYS-2010-935 (November 18, 2010) and the publication “Production of isolated Higgs particle at the Large Hadron Collider Physics” (Letters B 683 2010 354-357), we studied the γγ invariant mass distribution over the range of 80 to 150 GeV/c2. With 37.5~pb−1 data from 2010 and 26.0~pb−1 from 2011, we observe a γγ resonance around 115~GeV/c2 with a significance of 4σ. The event rate for this resonance is about thirty times larger than the expectation from Higgs to γγ in the standard model. This channel H→γγ is of great importance because the presence of new heavy particles can enhance strongly both the Higgs production cross section and the decay branching ratio. This large enhancement over the standard model rate implies that the present result is the first definitive observation of physics beyond the standard model. Exciting new physics, including new particles, may be expected to be found in the very near future.See: http://cdsweb.cern.ch/record/1346326?
Update: Jester is up late with some comments here.
Update: Tommaso is skeptical here.
Update: It should be made clear that, while members of ATLAS work here at Columbia, I have no connection at all to them, and they had nothing to do with this. The source of the abstract posted here anonymously as a comment is completely unknown to me. The question has been raised of whether I should allow this kind of material to be posted to this blog and I think it’s a serious one that I have mixed feelings about. On the one hand, ATLAS has legitimate reasons for keeping this kind of information private, on the other, it’s the kind of information that traditionally has sooner or later circulated outside a collaboration in one form or another. As an example, in my graduate student days back in the early 80s, I remember Carlo Rubbia telling a large group of people at the departmental tea about how his experiment had the top quark “in the bag” (actually, they didn’t…).
I’ve generally taken the point of view that it’s not my job to stop rumors, but rather to put out accurate information about them when available to me. But blogs do raise all sorts of issues, and they’re likely to keep coming up. I’m curious to hear if my readers have any wisdom to share about them.
Update: Via Slashdot, some more comment about this, including disclosure of another vector of information transfer out of ATLAS:
Someone left a copy of the note on the printer in my office building. (I work on CDF at Fermilab, but there are others in the building who work on ATLAS at CERN.) The gist of the article is that they found a bump in the diphoton mass spectrum at a mass of ~115 GeV. If the Higgs exists, it is expected to produce a bump in that spectrum, and 115 GeV is a very probable value for the mass of the Higgs. (Experiments at LEP ruled out masses up to 114 GeV, but a mass as low as possible above that fits best with other measurements.)
Now, the inconsistencies: The bump that they found is ~30 times as large as the Higgs mass peak is expected to be. However, due to field theory that I don’t want to get into here, the Higgs peak in this spectrum could be larger than expected if there exist new, heavy particles that we haven’t discovered yet. The latest published result from CDF sets a limit of about 30 times the expected rate at 115 GeV in the diphoton channel. (Yes, this means that, if you’re optimistic enough, there’s just enough wiggle room to fit a Higgs in there while accommodating both measurements.)
The internal note is very preliminary and uses a crude background estimate; I’ll have to see a more thorough analysis before I make any judgment on it. We shouldn’t have to wait very long; I expect that after this leak, they’ll be working overtime to push out a full published result as soon as possible.
Update: Since I don’t traffic in rumors of dubious source, you’ll have to go here to get the latest rumors from someone younger who knows about this whole Twitter kind of thingy…
The note says that a revolutionary new particle will appear soon, something that happens maybe once every 20 years. It also says that the the standard Model is about to be superseded, something that has been touted for 20 years too.
It’s like saying “The world will end next week!” or “A new continent will be found in the Pacific Ocean tomorrow!”
The flavour of it is similar to a pep-talk at a political rally just before an election.
If someone has access to the note, perhaps they could send the pdf to peter and he can make it public via this blog.
Harold Camping [http://en.wikipedia.org/wiki/Harold_Camping] predicts End Of The World Through Rapture for in exactly one month [21st May].
Coincidence? I think not!
A question for experts: is this kind of signal consistent with Tevatron data? Looking at
http://moriond.in2p3.fr/QCD/2011/MondayMorning/Cooke.pdf
I see an overall combined limit at 115 GeV of 1.5 times SM, and in the specific channel mentioned here (115 GeV Higgs to gamma-gamma) independent limits of about 20 times SM from D0 and CDF. Can a higher production cross-section at LHC than at the Tevatron explain this?
This is probably an April 21st fool’s joke…
If it’s true, it likely means that there is a fourth generation.
Lets draft a press release that this is an experimental test for string theory! 🙂
I can’t swear but I believe that when the different final states are combined to quote ‘The SM Higgs Bound’ the SM branching fraction weights are used. If for some reason the Higgs were SM-like except for the gamma-gamma final state (which I think is non-trivial especially as the glu-glu channel cannot be too much changed) then one needs to look only at the search in the specific gamma-gamma search channel. As Peter points out the bounds from Moriond for masses near 115 GeV are ~20x the SM value.
A Tevatron/LHC experimenter should comment further.
Peter, according to the abstract the search is along the lines of that proposed in “Production of isolated Higgs particle at the Large Hadron Collider Physics” (Letters B 683 2010 354-357), which is “semi-exclusive” Higgs production. This is quite different from the searches so far at the Tevatron, which are inclusive, i.e they search for ppbar -> H + X, where X is anything. So this could explain why the previous exlusion limits do not apply.
Of course, we have no real details of the search or analysis…
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OhDear,
I’m no expert, but that paper they refer to strikes me as odd on several counts, including its promotion of the idea of “considering the LHC as a Pomeron collider”, and the fact that it looks like it was never posted to the arXiv.
From the abstract, it certainly sounds like all they’re doing is looking for two photons and plotting their invariant mass. If so, that’s comparable to the Tevatron searches, right?
If it coupled so strongly to gamma gamma wouldn’t it have been seen at LEP ? Is this size signal consistent with the Higgs “hint” seen at LEP ?
I am afraid I think this is a cruel hoax.
Paul Wells
Four generations aren’t enough for a factor of 20. One could do it with five, but that would require something else as well to take care of the precision Electroweak measurements.
Paul,
Good question. They’re claiming to be at 115 GeV, not far at all above the LEP limit.
Tim: even 5 isn’t enough as the Hgg coupling increases BUT there is a destructive interference with the WW contribution in the gamma gamma case shrinking it!
I’ll fuel the controversy a little bit.
Looking at the Moriond talk by Markus Schumacher (ATLAS), it says that they have a limit of 40 times the expected Standard Model rate (see figure on bottom right of slide number 4). This is with the the 2010 data of 37.6 pb^-1.
http://indico.in2p3.fr/getFile.py/access?contribId=76&sessionId=1&resId=0&materialId=slides&confId=4403
However, if you look at the data (bottom left plot), it is much flatter than what they predict. So what they could be doing in a reanalysis is using a sideband, where you would estimate by extrapolating from outside the peak that the two bins around 115 should have 10 background events each (20 total). That leaves roughly 14 signal events which would give a significance of 14/sqrt(20) = 3.13. With the additional luminosity of 27 pb^-1, scaling up these numbers would give a significance that goes to sqrt(1+27/37.6) = 4.1, very close to the 4sigma the note claims.
Thanks for the quick analysis Spencer…I showed the same panel to a VERY famous , prize-winning experimenter some time ago 7 HE thought there was a bump there in the 35 pb^-1 data set
Assuming that it’s right, what does this do for SUSY?
Amos,
It would be a big confirmation for SUSY, but might also imply the existence of additional matter besides the superpartners.
*IF* this is right, all it says is that there is a bump in the gamma gamma channel at ~115 GeV. It says nothing about SUSY and seems difficult to explain with a Higgs since the production rate is so high.
*IF* the bump is the Higgs, then it does say a great deal about SUSY since this is exactly where SUSY says it should be. The high production rate can be explained if there are extra heavy states which also couple to the Higgs.
If it is a Higgs, the enhanced production cross section could just be an upward fluctuation. If I remember it correctly, top quark production cross section was also too high initially…
Well, MSSM SUSY needs the Higgs below ~130 GeV. If there really are a bunch of extra states (like a 4th generation or more) then this limit no long applies & one can’t say that SUSY predicts ~115 GeV. Also the additional states would change the EW fits so that a light Higgs would then also not necessarily be prefered by the data.
@Eric: The problem is that CDF/D0 already limit the glu-glu-Higgs couplings from their searches in the WW* mode. You can’t add extra heavy states willy-nilly without screwing this up.
And I contend that a potential observation of a light Higgs does not confirm SUSY. Could be a coincidence. The observation of a sparticle (and the precise measurements of the terms in the underlying Lagranian) confirm SUSY.
So, if there’s a fourth generation, am I right in remembering that the enhanced production rate is about a factor of ~9 for 300-400 GeV fourth-generation quarks?
You get a factor of ~9 enhancement in glu-glu-Higgs with a 4th generation, but then you also get a factor of ~2 suppression in gamma-gamma-Higgs coupling.
This is an internal, un-vetted, un-reviewed ATLAS document. It hasn’t been released for public consumption precisely because it hasn’t been reviewed or vetted.
You’re wasting your time spinning your theoretical wheels on such tripe, and it doesn’t serve any purpose other than the blogger’s desire for hits.
Daniel,
This blogger actually isn’t very interested in hits, this isn’t a commercial site. Rumor-mongering has its own rewards though, and this sort has a certain educational value (I learned some things about Higgs searches in general this evening).
I’m shocked to hear that ATLAS internal documents contain tripe!
Like all internal, un-vetted documents, there is the significant possibility for errors. I imagine if I ruffled through a theorist’s unfinished work I’d find some shocking results which turn out later to be wrong…
I’m all for openness, but then we need to be consistent, so you’d see how often ATLAS sees wiggles in the data which appear to be interesting, but are then quickly understood to be run-of-the-mill errors in background calculations….
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Madame Wu is the best scientist in the world, and one of the most influent women in USA.
She discovered already twice the Higgs in LEP in ALEPH.
Her famous words when anybody tried to argue on the consistency of arguments and data were:
“What do you prefer, to have a signal or not?”
So she is now simply rediscovering her Higgs at 115 (that was 10x what expected also at that time).
Peter,
you rightly chide others for blogs and press releases which allow others to gain a distorted view of research findings. Given that this “Higgs discovery” seems based on an internal ATLAS note and that it is not an approved and well checked result, you’re as guilty of hype dissemination as those you criticise.
Experiments spend a huge amount of time and effort in getting results right. They have the right to announce a result only after they’ve performed due diligence. Circumventing this with rumours needlessly damages their hard-earned reputations and does nothing for the advancement of science.
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Hi all,
just to mention that I also covered this in my blog too, after reading Peter’s post above. See http://www.science20.com/quantum_diaries_survivor/did_atlas_just_see_higgs-78316 .
In any case, I think the signal is a fluctuation. Their significance is overblown by tuning cuts, and their estimated look-elsewhere effect (the trials factor due to not knowing in advance what to search for and where) is much smaller than what it actually is.
I also want to comment on the use of these “rumors”. I think they are valuable for attracting the attention of outsiders. However, insiders should not be attracted into this game too much…
Cheers,
T.
This is likely trigger effect. If the have any trigger cuts around 110-120 GeV, this is threshold behaviour of not very well simulated trigger. ATLAS is famous for its approximations in MC, when they are using average efficiencies for various kinds of particles across large eta-phi areas instead of full detailed MC. So, it is possible to gain whatever bump you want in the areas near the trigger thresholds – they just didn’t simulate them properly.
Tim: “Four generations aren’t enough for a factor of 20.”
Tom: “even 5 isn’t enough”
Is this specifically for 300-400 GeV fourth-generation quarks? What if the 4th generation was heavier, e.g. 600 GeV?
@Visitor
Can you point me towards an ATLAS physics publication in which a detailed trigger simulation isn’t used ?
@Tommaso
I don’t share your view that this is all good publicity. The field has suffered from a number of hyped up non-discoveries in recent times, eg WIMP dark matter, dubious resonances etc. The public may well be getting sick of the particle physics community crying wolf. I certainly am.
Chris: Once the mass for the chiral quark is larger than of the top quark’s, then to a good approximation the explicit value doesn’t matter so 300 or 600 GeV makes little difference here. However, there is a perturbativity bound on the couplings of these heavy objects so they cannot be heavier than ~600 GeV.
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@Visitor: Oh please. ATLAS is, if anything, famous for using (slow) full simulation for everything. Perhaps you are confusing “efficiency” with “efficiency systematic uncertainty”.
I find this discussion rather distasteful: publicizing a collaboration’s internal documents, with absolutely no context, is a profoundly unprofessional thing to do – we’re here to deliver quality science, not to entertain people with exciting rumors. Shockingly, while initially exploring and considering the data, we may use looser terms and standards when talking to each other than we would use for an external publication.
Steven,
To “hype” something, you have to put out misleading information about it. My goal has been to provide accurate information about topics of interest, and I think that’s what I did here, with the posting and subsequent discussion providing to anyone interested a pretty accurate picture of what is going on.
The question of what I should do with different categories of information that either gets sent to me or posted on my blog is a legitimate one. This may be a borderline case, but I don’t think the problem here is “hype” as long as the information made available is accurate.
I think I’m “pro-rumor”. As you say, they’re educational, and it gives us something to discuss during the current drought of actual discoveries. If the rumor turns out to be bunk, I don’t really see any harm done.
I’ve seen the note. It is clear that they see something with cross sections largely above what is expected in SM. It is also clear that there is no tengible proof shown that this is not a fluctuation of the QCD background. The QCD with 2 prompt photons is not well known area. The estimations of the background is purely data driven based on the side bands estimation.
What is nice is that the analysis is quite simple, no Neural Network, no complicated cuts and games.
I think as a taxpayer I have a right to know what is going on at an early stage. Peter and others are doing a valuable service that arguably should be done by CERN itself being more open. This type of blog shows that science is an exciting, risky, and difficult human activity where mistakes are often made. What is the big problem with that ? Please credit us taxpayers credit with enough intelligence to filter out the gold nuggets from the crud.
Paul
I would agree it’s a “simple” analysis, but the devil is in the details. If they grew enamoured with the fluke they saw in 2010 data, they probably played around with cuts enough to get something out of nothing.
As for the bigger issue of whether this is good or bad, and despicable or reasonable, I have written at length on the topic, but let me point out that in this case indeed we are talking as if this was an atlas result when it really looks like the work of four people working in isolation. At least that is the impression I got.
I must say that if I were in ATLAS, I would not be very happy of the way things have turned out… But I would never blame the bloggers, who do nothing but report what is already out there. They should blame their own collaborators for leaking the material.
Best,
T.
@Paul Wells
As a taxpayer you have a right to the best science and value for money. Why does this mean that you need to read internal documentation and look at results as they are being produced/disarded/prepared for publication ? Don’t you think that scientists should be allowed to have private discussions during data analysis ? To the best of my knowledge there has never been a climategate-style scandal in particle physics. There are no “secrets” but scientists rather like the right to talk openly at work without the world listening in. Furthermore, collaborations are usually in healthy competition with each other. They wish to develop their own techniques to, eg, suppress backgrounds to steal and edge on the opposition. There won’t be too much of that in the true “open access model” which you propose.
Peter,
you put out information which suggests that ATLAS has found the Higgs and hosted the subsequent discussion/speculation. That pretty much fulfills the definition of hype:
“excessive publicity and the ensuing commotion”.
Tom, thanks.
This is NOT a PUBLISHED PAPER. It’s a COM note.
Anything, especially garbage, can be published as a COM note. It’s internal to the ATLAS collaboration, NOT REVIEWED by anyone, NOT APPROVED.
An approved result is signed by the entire collaboration, namely more than 2000 people.
Seeing this on a blog is a shame. The person who releases this paper is not worth being called a scientist. Makes me sick.
Steven,
Read what I wrote introducing the topic:
“Best guess seems to be that this is either a hoax, or something that will disappear on further analysis.”
I partly agree with your response to Paul Wells: scientists should largely be allowed to do their data analysis in peace, without the world looking over their shoulder. People need to have some privacy to make mistakes. But I don’t buy the argument that scientists won’t come up with better experimental methods if the competition is going to immediately get access. A better argument for secrecy would be that leakage of information between two experimental groups makes their results not completely independent, whereas that’s a very desirable characteristic.
One thing that occurs to me is that the scale of the LHC experiments is something new. If everyone in ATLAS has access to this note, you’re talking about 3000 people, no? Maybe a third of the world-wide experimental HEP community? If you’ve already got 3000 people looking over your shoulder, you’re not exactly able to make mistakes in private. I’m not well-informed about ATLAS procedures, so it surprised me to hear that results from a small group of 4 people were being immediately broadcast to the entire collaboration, before a smaller, more specialized group had done some vetting.