Sunday, August 21, 2011 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Lepton-Photon 2011: Higgs results

New: The live webcast from the Bombay conference is on this page. The schedule is here. The Higgs talks were delivered now on Monday early morning, Prague Summer Time (they're over by now). Check the current time in Bombay: yes, it differs from your time by an odd multiple of 30 minutes. ;-)

The fresh new ATLAS Higgs plots: click to zoom in.

After the Higgs talks: In general, the previous Higgs signals have weakened. Some more details: A 35-minute introductory theoretical talk on the Higgs physics was followed by three 20-minute talks by ATLAS, CMS, and Tevatron. ATLAS - see their fresh new Higgs press release - excluded everything at the 95% level except for 114-146 GeV, 232-256 GeV, 282-296 GeV, and above 466 GeV. No new details about the preferred masses inside these intervals, despite 2/fb of data in some channels.

The newest CMS Higgs graph: I like the eye-catching localized 2-sigma excess at 119 GeV. And there's also the larger - but expected to be larger - excess around 140 GeV.

CMS - see their newest press release as well - has mentioned that the p-value for Higgs to gamma-gamma grew deeper, more significant, near 140 GeV but more shallow near 120 GeV. Nothing is seen in the tau-tau channel - which will however grow important in the future. The speaker explains the WW channel ending up with 2l 2nu; then ZZ "golden" channel with 4 leptons. Many combinations are shown. In the CMS p-value, the 120 GeV is actually slightly deeper than for 140 GeV - difference from the gamma-gamma channel itself. Surviving intervals (from the 95% exclusion) are 114-145 GeV, 216-226 GeV, 288-310 GeV, above 340 GeV - different small hills than ATLAS.

The deviations grew weaker since the last time. Fascinating new limits on tan(beta) in MSSM to be presented later. The intersection of the CMS and ATLAS allowed intervals are 114-145 GeV, 288-296 GeV, or above 466 GeV.

Tevatron has collected 11.5/fb or so and will close on September 30th. They may need another year to present the final results and they will only based on 10/fb. Lots of technicalities on their work - which I won't discuss because things are changing at the Tevatron much more slowly than at the LHC. Multivariate techniques have improved the dataset by 10-20 percent. Some LHC Working Group were adopted recently. The final graphs show upper limits that almost don't differ from the expected ones. They're totally uninteresting. The weakness of the Tevatron relatively to the LHC is obvious from many technical results - like the exclusion of the Higgs in 4-generation models which is much more stringent at the LHC. The Fermilab did some good work on SUSY Higgs - but their limits have been beaten by the LHC, too. Both D0 and the CDF do see some excess in the "bbb" channel - suggesting a somewhat large tan(beta) - but you shouldn't view it as some new independent news. It's pretty much the same excess that's been discussed on this blog many times.

Originally posted on August 18th, 10 am

The Lepton-Photon 2011 conference begins on Monday, Aug 22nd, and ends on Saturday, Aug 27th in Bombay.

The ATLAS blog suggests that their collaboration will present experimnetal results based on 2 inverse femtobarns of data - doubling what we could see just a month earlier (in Grenoble, EPS-HEP 2011) and multiplying by ten what we could see three months ago.

So there's surely some new potential to learn new things about the Higgs boson, supersymmetry, or maybe other things. And some of us will surely try to produce combinations of various new graphs from diverse collaborations, too.

When it comes to the Higgs boson, there are two most likely regions where it could show up - one of them is near 116 or 119 GeV or, more generally, 115-130 GeV; the other one is heavier, near 144 GeV. The existence of both bosons is also plausible - and would be a strong hint in favor of the two-Higgs-doublet supersymmetry.

This blog was the first website on this blue, not green planet that identified a peak near 144 GeV as a rather likely mass of the Higgs boson. I still believe that it's more likely than not that there is a Higgs below 120 GeV (and maybe others). The hints near 144 GeV are easier to be collected so there's a bigger excess (in the number of standard deviations) near 144 GeV; on the other hand, the possible Higgses below 120 GeV are more safely avoiding the exclusion so far for the same reason. ;-)

So it is up to you how you combine these two arguments - positive and negative ones - and what relative weights you assign to them and what to conclude about the relative likelihood of the two masses at this point.

Just to be sure, the "doubled integrated LHC luminosity every month" was the exponential growth we've encountered for quite some time. This amazing progress is likely to slow down in coming months. I don't expect that the total luminosity will jump from 2.5/fb per detector now to more than 5/fb at the end of 2011, at least not substantially.

Prof Matt Strassler of Rutgers has a website where he has posted various articles about supersymmetry, its detection, the Higgs boson, addressed to technically advanced laypersons or auto-didacts, so you may want to check the website.

Mass of the antiproton: CPT works at 1 ppb

In recent 3 days, the ASACUSA experiment at CERN announced its accurate laser measurements of the antiproton mass. It agrees with the proton mass at the accuracy of 1 part per billion. The CPT symmetry which almost certainly holds exactly implies that matter and antimatter - whenever they can be distinguished by charges to be sure that you made the "anti-" operation correctly - have exactly the same mass.

In the near future, they paradoxically expect to be able to measure the antiproton mass more accurately than the proton mass! Our knowledge of the antiworld (LHC song) could be better than our knowledge of this world - of the particles we routinely encounter. ;-)

Just compare the measurement of the antiproton mass with some of the spectacular claims about the top-antitop mass difference. It's almost the same thing but CDF at the Tevatron claimed that the antitop mass differs from the top mass by 3 GeV or so - by two percent.

Try to invent a reason why the top and antitop masses would differ by 2% - but the analogous proton-antiproton mass difference (which may be affected by the top-antitop differences as well) would be smaller by more than 7 orders of magnitude. I don't say that it's strictly impossible to invent such a mechanism but it is probably going to be very awkward.

Claims that someone observes CPT violation are extraordinary claims and they require extraordinary evidence. So if one measures the top-antitop mass difference to be nonzero at a 2-sigma or 3-sigma level (by 3 GeV), he should say that "our measurements were rather inaccurate; our observation of the mass difference had the error of 3 GeV".

Add to Digg this Add to reddit

snail feedback (2) :

reader O Senhor dos Queijos said...

weather-ice summer 2011,

a high-pressure cell persisted over the northern Beaufort Sea, promoting ice loss. This weather pattern broke down toward the end of July, slowing ice loss but spreading out the ice pack, making it thinner on average. The weather has now changed again, bringing another high-pressure pattern. Winds associated with this pressure pattern generally bring warm temperatures, and tend to push the ice together and reduce overall extent. In the Kara Sea, the combination of a high-pressure cell with low pressure to the west has resulted in strong northward ice movement, pushing the ice pack away from the coast and reducing ice extent.

and deplaced some southern cell's

a nice warm and rainy summer

quasi remembers Praha

bad for turists but....
refreshing for madrileños

reader Kamil said...

Looks good, maybe it could achieve another minimum extent record in september.