CMS . . . exclusion from 130 GeV up. Excess seen at about 123 GeV of 2.5 Sigma.
The 123 GeV peak is heavier than the 119-121 GeV peak that had been rumored in the past week, and is close enough, once rounding error and statistical uncertainty are considered, relative to the ATLAS result.
Both the CMS and ATLAS results show surprising wide decay widths in their diphoton results, about 6 GeV (which is about three times that of the top quark), which are overlapping but shifted from each other, although this may partially be an artifact of thin data sets rather than an accurate measure of the true decay width of the Higgs boson.
The 2.5 Sigma excess is accompanied by another not quite 2 sigma excess at 137 GeV but given the much better resolution of the data there, a real Higgs boson at that mass ought to have a much stronger signal than sub-two sigma by now, so it is still in the 95% confidence interval exclusion range. "The CMS ZZ->4l clearly rules out the 140 GeV possibility, but has an excess at lower mass."
The ATLAS experiment has about a 2.8 sigma Higgs boson signal at about 126 GeV. ATLAS sees a potential signal, not quite 2 sigma, driven by data from the ZZ->4l channel at roughly 240 GeV, but is within the Brazil bands everywhere heavier than that up to 500 GeV and in that channel at all lower masses. There are results in excess of 1 sigma in the 120-130ish GeV range from ATLAS in this channel but nothing that by itself confirms the diphoton result that ATLAS is seeing (pre-announcement rumors states that the diphoton result involves just three events but is significant because there is nothing else that can create that signal). The combined ATLAS data is outside the two sigma Brazil bands from about 123 GeV to 129 GeV with a peak at 126 GeV. Thus, the results from ATLAS are just barely consistent with those from CMS. (These are the two main experiments at LHC looking for a Higgs boson; the only other place doing high energy physics Higgs boson searches finished its work earlier this year when Tevatron was shut down for lack of Congressional funding due to its inability to add much to LHC findings with its less powerful experiment.) CMS doesn't see much significant in the WW channel which has far more background noise making a signficant observation harder to obtain.
The viXra combined plot from the diphoton channel is significant in mid-120s GeV range, with no other SM light Higgs boson masses in the running. "[T]he CMS combined plot . . . gives a clean indication for no Higgs about 130 GeV [and up] and the right size signal for a Higgs at about 125 GeV, but there is still noise at lower mass so chance that it could be moved."
Per Lubos: "In ATLAS combination with 2.1 sigma (locally) from ZZ and 1.4 sigma (locally) from WW, the combined excess near 126 GeV is 3.6 sigma locally and 2.3 sigma globally (with the look-elsewhere effect correction)[.]"
Resonnances reports: "CMS excludes Higgs down to 127 GeV. ATLAS also excludes the 112.7-115.5 GeV range" and that in the diphoton and quadlepton channels that there is a "mass resolution of order 2 GeV."
The excess is seen by both experiments and in each of these channels. The excess in H→γγ peaks around 124 GeV it CMS, and around 126 GeV in ATLAS, which I guess is perfectly consistent within resolution. In the 4-lepton channel, ATLAS has 3 events just below 125 GeV, while CMS has 2 events just above 125 GeV. It's is precisely this overall consistency that makes the signal so tantalizing.
In sum, the announcement seems to show a Higgs boson in the mid-120 GeV mass range, with a significance on the order of between 3 and 4 sigma for the combined results, but the coincidence between the CMS and ATLAS results isn't quite as precise as one might hope in either estimated mass or signal significance, and confidence in the result is also reduced by the fact that the signals in some of the other channels at this mass range are not as strong as one might wish to see, although there do seem to be some individually insignificant but collectively notable excesses over expected background in the noiser channels.
There are a few other fairly weak bumps in the data, but they are not terribly consistent with each other, so they are probably just flukes. Low experimental accuracy at the low end of the mass range (ca. 115 GeV-121 GeV) leaves the data there particularly inconclusive and uninformative.
From a numerology perspective, the results a consistent with a Higgs boson mass equal to the W+ + W- + Z boson masses divided by two, which is about 125 GeV, but are probably a tad heavy to be equal to half of the Higgs field vacuum expectation value, which would be 123 GeV.
Generally, in physics, two sigma results routinely disappear with more data and rarely amount to anything, three sigmas results pan out about half the time, and five sigma results are considered lasting and permanent discoveries. Today's announcement nudges the likelihood that a light Standard Model Higgs boson exists to somewhat better than 50-50, but as promised, is inconclusive at this point. The fact that there are strong thoeretical reasons to expect that a light Standard Model Higgs boson (or an indistinguishable light SUSY Higgs boson) exists nudges the odds against a Higgsless or heavy Higgs only model being correct a little higher.
Of course, this is only the first year of what will be more than a decade of experiments at LHC. A year from now, the inconclusive results that we received today will almost surely be confirmed or denied and the LHC will move on to looking for other kinds of new physics.
I've been fortunate enough to be alive while quite a few of the fundamental particles of particle physics were first observed (and even while a few of the higher atomic number atoms in the period table were first synthesized and some of the key equations of the Standard Model were developed). A Higg boson could very well be the last one discovered ever, or at least, during my lifetime. Assuming that a Higgs boson is discovered at this mass, the Standard Model of Particle Physics will have no missing pieces, although the masses and transition matrix for neutrinos will still be somewhat indefinite and the question of whether neutrino masses are Majorana masses or Dirac masses will remain unresolved (my sense is that the later is more likely, but see-saw mechanisms are very popular in theoretical circles).
Quote of the day:
Kea said... Wow! Fairies exist! Amazing work from ATLAS and CERN, and thanks for the early report.
FWIW, I rather like Kea's mocking terminology that calls Higgs bosons "fairies" and the Higgs boson, "the fairy field." It certainly beats calling it the "God particle" hands down.
UPDATE: Gibbs has his combined plot estimates out and they are very convincing, particularly after LEP and Tevatron data are included and one looks at the signal to not signal probability charts. I'm pretty comfortable that the Higgs boson find that is currently a 3 sigma result at about 125 GeV +/- a couple GeV is real. The combined data also reinforce the conclusion that this will be the only Higgs boson detected in the under 500 GeV mass range (at least) based upon the data in the combined plots from all four experiments, despite modest "bumps" in specific channels at certain other mass ranges - in the overall picture they fade to become mere statistical noise.
This is a huge triumph for the scientists who predicted this discovery back in the 1970s. It completes the Standard Model. No particle predicted by it is missing, no particle (or force, other than gravity which is beyonds stated scope) which is not predicted by it, has been discovered. There is no replicated high energy physics experiment that is significantly at odds with its predictions (the lone significant deviation at the moment is OPERA's superluminal neutrino result).
At the end of the 1800s, scientists thought that they had conquered all of the fundamental rules of nature, although there were physical constants to be honed and applications of those rules that had not been worked out. Five generations later, we may very well have actually achieved that result.
I am increasingly inclined to conclude we will find no supersymmetry, and that we will ultimately be able to explain dark matter with the physics that we already have in hand. When we someday find a way to integrate general relativity and the Standard Model that it will turn out to be a dotting of i's and crossing of t's moment rather than a discovery that provides any meaningful new phenomenological insight. With all of the underlying pieces having pretty much come together, we may just a mathematical trick or two away from the day when that formulation of quantum gravity becomes possible and the job of theoretical physicists becomes merely a matter of making it all look as pretty as possible.