Some more detail on Higgs rumors I’ve been hearing recently. Evidently the latest ATLAS data shows an excess in the gamma-gamma channel around 126 GeV, of the size expected if the Higgs is there, and CMS is also seeing an excess (2 sigma?) around 125 GeV in the same channel. I haven’t heard anything about confirmation of this in other channels. Independently, someone has posted a similar rumor at viXra log, and Philip Gibbs is writing about it here. This looks to be still not a conclusive Higgs signal, but the closest thing yet. More details may or may not emerge before the public talks on December 13.
Update: Latest rumor is that the significance of the ATLAS gamma gamma bump is almost 3 sigma.
Update: This morning’s rumors are a 3.5 sigma 126 GeV excess at ATLAS in the ATLAS-only combination, and 2.5 sigma at 124 GeV for CMS. Heuer’s message to all CERN personnel says the December 13 announcements will be “significant progress in the search for the Higgs boson, but not enough to make any conclusive statement on the existence or non-existence of the Higgs.” Presumably they’re waiting for 5 sigma before claiming conclusive proof.
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So if there is a 3.5 sigma at 126 GeV with the current ATLAS analysis, and a 2.5 sigma at 124 GeV for the current CMS analysis, then when the combined analysis of both ATLAS and CMS is done next year which has been mentioned here previously– if the signals are real, what sigma would one estimate the combined analysis could probably get up to with this existing data? (Is this even a sensible question?)
Traveling today, will probably write something about that tomorrow.
Philip Gibbs is the expert on this….
Coin, about 4.3 sigma.
Interesting rumours, indeed, and I am confident
the Higgs will be found in the range 122-132 GeV, having
predicted its mass together with the top quark mass
in a composite model, before either top or Higgs were
detected. But I’ld point out there were similar rumours
of an excess in the b anti-b channel indicating a Higgs
in the range of 130-140 GeV just a couple of months back
(personal communication from W. Marciano). It was a similar
deal, a couple of sigma each in CMS and Atlas, which added
to a bit more than 3 sigma. It went away of course.
My last look at the 2 gamma data, with about
half of the total data set analysed showed points above
and below the theoretical continuum, and no
sign of a bump whatever. The SM Higgs width at this
mass is so small that I don’t even remember the number
but I believe it’s on the order of 1 MeV. So in this case
the width of any bump in the 2 gamma mass spectrum
will be determined by detector resolution, on the order
of 5 GeV. There was an extra factor of two available
in the integrated flux not analysed at that time, but
that only gives 40% better resolution of any bump
at 125GeV. So I can’t believe this will be conclusive.
A SM Higgs this light just escapes the vacuum
stability and metastibility (due to finite temperature
effects in the early universe) if new physics only
appears near the Planck scale.
So it’s premature for Kane and the supersymmetricians
to be rejoicing, I think. They should rather be worrying
about the absence of supersymmetry at 95% confidence
level, below about 1 TeV. Exciting times!
The Higgs mass (125 GeV) was calculated, along with other parameters of the Universe, based on the model of Expansive Nondecelerative Universe, see our paper J. Šima, M. Súkeník, Nondecelerative Cosmology – Background and Outcomes, published in Pacific Journal of Science and Technology 12(1), 214-236 (2011) and included references.
I suppose it’s only polite to leave references that can be checked, when one claims to have predicted something, so here are links to my various predictions of the top and Higgs masses.
I seem to remember that the major uncertainties at the time these predictions
were made was the value of the strong coupling at the Z mass. And we were using one loop beta functions for the evolution. But no theorists I talked to at the time believed in a top mass as a high as 160 GeV.
Standard-model bosons as composite particles
Phys. Rev. D 43, 2361–2368 (1991)
Prediction: Higgs ~140 GeV, Top ~ 160 GeV
(Top and Higgs Masses in Dynamical Symmetry Breaking
Prediction: Higgs ~ 125 GeV, Top 175 GeV
Prediction: Top∼180(185) GeV and Higgs ∼130(135) GeV.
sorry if this is a well known fact, but how correlated would the errors from Atlas and CMS be? Presumably there are shared system errors?
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the uncertainties of the two experiments are mainly statistical at this stage, and completely independent. There is, in truth, some strange common choice for background shape parameterizations (both experiments are using Bernstein polynomials for the background in their H->gamma gamma searches, which is odd at the very least, since the choice is not particularly bright), but most of the stuff is completely orthogonal. In particular, backgrounds in the gamma-gamma are data-driven, so no MC dependence is there.
Well I guess now that I’m out of academia, I can comment without stepping on anyones toes – as I’ve had not direct contact with experimenters working in the field in 10 years!
Anyway the photon-photon channel is interesting, because only spin 0 particles can decay into two photons. So if a bump is seen in the photon photon mass – then it must be some kind of spin 0 particle, e.g. the Higgs.
So its just how big is the bump over the photon photon background. Alass don’t have the code I once had, so can’t do some simple calcuations of the various cross sections. Nice thing is though that for signals like this the significance of results builds quickly. So its at 3 sd now – give it another 6 months or so (or rather the next run), and it should be a very significant signal then.
Interesting though to hear about my PhD subject coming back to life …
Oh yes – what I also should have said, is whats interesting about this channel is it only demonstrates a higgs in the electro-weak channel; e.g. responsible for mass of the W and Z; but non necessarily responsible for generating quark masses.
To establish the latter they would need to look for the b bbar branching ratio of the Higgs, and that will be a very messy signal down at 125GeV – probably can’t be seen in all the muck.
So does make it an interesting time for high energy physics …
Sorry to contradict you, David. How do you think the Higgs is being produced in the first place?
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Hope you don’t mind my extensively quoting from your blog here:
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Sascha Vongehr writes
> Low higgs max expected
> Universe about to decay – possibly due to experiments in the LHC
> Nobody should care because Many Worlds theory
I must confess I have rarely read anything weirder outside the most psychotronic layers of the Internet Subconcious’ Alluvials.
An interview with Joe Lykken, with the cherry-on-top comment to that “brilliant” article from Kane: “I would say it would be an example of a successful connection between string theory and experiment.”
Tuesday will be mostly a confirmation that there is enough data to narrow search to the 115 to 130 range with some hints of a signal (likely around 125). These hints will be less than 3 sigma.
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Only just check back here – taking my mind back 15 years to when this was fresh …
Higgs of about this mass at pp colliders are mainly produced by a pair of W or Z bremed of quarks in the t channel – these then merge to form the Higgs. So this is sensitive to WWH and ZZH couplings.
There is also a contribution from gluon fusion, via a top loop. That is sensitive to H t tbar coupling, and so mass generation for quarks. From what I recall though at these masses its t channel vector boson fusion which dominates – my memory though could be wrong, so I’d be happy to be contradicted ….