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:
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.
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…