New results about the Higgs should appear over the next day or so, perhaps first here and here. First to appear is the CMS tau-tau result which is a signal strength of .72 +/- .52 the SM value.
Will update this posting with the results as they appear.
I guess the rumors were right: no update from ATLAS for gamma-gamma, they’re just presenting the earlier data: signal strength of 1.8 +/- .5 times the SM value. “Ambitious campaign underway to include a larger data-set.”
ATLAS WW channel signal strength is 1.5 +/- .6 times the SM value (see here). For some reason they are only using 2012 8 TeV data, not combining with the 7 TeV data.
Atlas tau-tau signal strength is .7 +/- .64 times the SM value (see here). Very similar to the CMS value. They are not yet sensitive to the bb channel, where the Tevatron has the advantage and has evidence of a signal.
Update: All new results are out now, but rather anti-climactic since neither CMS nor ATLAS is reporting new results for the channel with the strongest signal (gamma-gamma), where the signal strength may be anomalously high. ATLAS is also not reporting for the other high statistics channel (ZZ). CMS is, with signal strength .8 +.35/-.28 the SM value. They also claim to rule out (at 2.5 sigma) the hypothesis that this is a pseudoscalar rather than scalar. Everything reported is in line with the SM, but for the most interesting numbers we may have to wait until next March (Moriond).
For much more details about all this, see Tommaso Dorigo here and here, Matt Strassler here and here, Philip Gibbs here. For primary sources, CMS here, ATLAS here, presentations here.
Update: For another excellent source, see Jester, who has the scoop on why ATLAS and CMS didn’t update some channels:
It came to a point where the most exciting thing about the new Higgs release was what wasn’t there 🙂 It is difficult not to notice that the easy Higgs search channels, h→γγ and ATLAS h→ZZ→4l, were not updated. In ATLAS, the reason was the discrepancy between the Higgs masses measured in those 2 channels: the best fit mass came out 123.5 GeV in the h→ZZ→4l, and 126.5 GeV in the h→γγ channel. The difference is larger than the estimated mass resolution, therefore ATLAS decided to postpone the update in order to carefully investigate the problem. On the other hand in CMS, after unblinding the new analysis in the h→γγ channel, the signal strength went down by more than they were comfortable with; in particular the new results are not very consistent with what was presented on the 4th of July. Most likely, all these analyses will be released before the end of the year, after more cross-checking is done.
Update: Two interesting workshops on prospects for a Higgs factory are being held at Fermilab this week. See here for one that is on-going, see here for Tuesday’s one-day mini-workshop on prospects for a muon collider Higgs factory. I’d never seen much before about the idea of using a gamma-gamma collider to study the Higgs, curious if that’s really technologically viable.
this all looks as if the experiments really might have a problem with the signal strength of the Higgs bump. Any rumors on whether the Higgs is disappearing or is confirmed?
The rumor about ATLAS is not that the signal is going away, but that they were worried about calibration problems due to seeing peaks at different masses in gamma-gamma and ZZ. It would of course be very interesting to hear more about what is really going on. I also hear that CMS has some concerns about their gamma-gamma signal, we’ll see soon how much they report.
Part of the problem here is probably the way they are trying to do blinded analyses, relatively quickly. If you don’t unblind until right before the date you need to have a result, when something confusing shows up when you unblind, you may not have time to figure out what is going on. One thing you don’t want to do is publicly release data that has some sort of consistency problem that you don’t understand.
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“Hangout with CERN: What’s new with the Higgs? + more LHC results”
Scheduled, 15. November, 17:00
there has to be a ZZ-top quark joke somewhere.
It seems to me that the SM is looking more and more like epicycle theory, in a good way: an ad hoc model with a limited set of parameters that quantitatively predict thousands or millions of observations to high accuracy. If this analogy bears out, it is bad news for BSM physics in general. There was never any beyond epicycle physics; Kepler did not observe any qualitatively new phenomena, but merely looked at the old data in a new way.
So if the gama gama signal is problematic or starting to dissapear, does that mean the Higgs is beeing undiscovered? Gamma was the strongest signal. Are they going below 5 sigma?
According to Jester, nobody cares if it’s 5 sigma or 11 sigma – Higgs is there. Decreasing gamma-gamma means that Higgs becomes even more SM-like, I think.
The new ZZ results that CMS reported strengthen even more the Higgs signal. If it was going away, it would be going away here too.
Given that the gamma-gamma signal was higher than the SM prediction, if it is a SM Higgs it’s not surprising that the signal would go down in the new data. If the reason for the earlier signal being high was not just a fluctuation but a systematic problem with the analysis, it’s also not surprising that with more data, this problem becomes more obvious. That most likely is all that is going on, with figuring it out a time-consuming business.
Of course, since we haven’t seen either experiment’s new gamma-gamma results, who knows, maybe there’s more to it. But I haven’t heard such rumors, and if there were a serious chance that the gamma-gamma would completely go away, that would be hard to keep 6000 people quiet about…
Wait. It was not the decrease in the gamma gamma that worried me but the size of it. I understood Jester to write that at CMS the signal decrease is substantial. Too much for comfort. To the point of beeing inconsistent with the July results. So one naturally wonders if these sytematic problems affect other channels as well.
I don’t see any reason to believe there’s a problem which is going to affect both of the main channels at both experiments (and CMS explicitly is claiming no problem in the ZZ channel by releasing that analysis).
This situation still looks to me like something not unexpected when you have a large collaboration with many cautious people trying to do an analysis on an extremely tight schedule. The way these people work they really hate to release something publicly unless pretty much everyone is happy that things are well-understood.
How significant is the difference between 123.5 and 126.5 GeV for relative probabilities of the different channels? I find it intriguing that they both feel something’s wrong with their analysis of gammagamma. As if the Higgs is different from the SM one in ways no one expected 🙂
PhyOrg says this is a hint towards SUSY.
Is there something to it?
The story says exactly the opposite
“The result further shrinks the region in which scientists can still look for supersymmetry.”
Please see the previous posting for extensive discussion of this.
got it wrong.
Much as I would like to see the construction of a muon collider, and the low mass of the Higgs perfectly suits such a machine, I very much doubt if any serious attention will be paid to building one unless the LHC uncovers anomalous behaviour of the Higgs which could only be investigated by a high-precision examination of Higgs properties and decay modes.
just one remark on big machines and hep. everybody knows which are the machines that helped the field to progress. now, we can check on the “inspire” database how many conferences have their name in the title. some outcome is,
Neutrino factory 25
Muon collider 16
Kamiokande or Super-Kamiokande 0 (=naught)
@ DB : don’t you think it’s a bit hasty to start building a muon collider ?
First lets use the LHC to its full potential, then when it starts becoming obsolete either tecnologically and/or scientifically we can begin financing a new collider. But I don’t think it will happen for at least a good decade. Or we could ask the Americans to build one. Europe has done its fair share building colliders, wouldn’t it be time for the American hep community to take up the slack ?
As far as I know, there’s no danger of anyone starting to build a muon collider soon, the technology is just not ready.
The more serious issue DB is alluding to is that of whether one can justify building any sort of Higgs factory if the LHC data on the Higgs shows no signs of a deviation from SM expectations.
Re: No funding for a post-LHC collider. Hasn’t the Japanese government all but volunteered to fund one if it’s placed in Japan? Unless that changes, isn’t the ILC or a muon collider probably a go? Or is there reason to worry that a no-obvious-deviation Higgs might be so uninspiring as to make even a large percentage coming from the Japanese government insufficient?