The Higgs discovery announcement will be at 9am next Wednesday. This is close enough that I can’t reasonably be accused of “subverting the scientific process” and ruining the LHC Higgs analyses by reporting the results here. Unfortunately, no source has provided me with these results yet, so that won’t happen anyway, at least not right now. However, I have learned the following, which may be of interest:
- On Monday at 9am Fermilab will try and steal a little bit of the LHC’s thunder by announcing some new evidence for the Higgs from the Tevatron data. This uses the channel of a Higgs produced with a W or Z, the Higgs then decaying to pairs of b-quarks. This is a channel where the Tevatron is sensitive to a Higgs signal, but the LHC isn’t (at the higher LHC energies backgrounds are too large).
- ATLAS and CMS each collected about 6 inverse femtobarns of data before the technical stop on June 18th, and they are rushing to get as much of it analyzed as possible. They are concentrating on the two most sensitive channels: H->gamma+gamma and H->ZZ->4l and are likely to have over 5 inverse femtobarns of 2012 8 TeV data analyzed in these two channels to present at ICHEP.
- There may not be any 2012 Higgs data from other channels presented at ICHEP. ATLAS will have a H->WW->lvlv analysis, but likely not ready for public release.
- To get the statistical significance necessary to claim a Higgs discovery, the experiments will be producing a combination of their best analysis of the 2011 data in all channels and the 2012 data in the H->gamma+gamma and H->ZZ->4l channels.
- There will be no CERN combination of ATLAS and CMS results publicly released. This is not because such a thing is hard to do (and I believe it is actually being done, just not released), but because of political reasons. I don’t much understand these, but this blog entry gives some of the kind of reasoning being used.
- With no CERN combination, attention will focus on Philip Gibbs at viXra log who in the past has produced reliable unofficial combinations of data, and is likely to do so again.
- With the discovery a done deal, the attention of physicists will focus on the question of whether the signal being seen is compatible with SM predictions, or whether this new particle has unexpected properties. Here the main two numbers to look for are the ATLAS + CMS signal size in each of the two most sensitive channels. To get these, you can do your own combination of the separate ATLAS and CMS numbers, or wait for Philip. The signal size is a product of the Higgs production cross-section and the branching ratio for the channel. I’ve seen estimates of the reliability of the SM prediction of the cross-section varying from 15% to 25% (see more here). The branching ratios are much more accurately known.
- Probably nothing new about SUSY at ICHEP. New SUSY analyses are being targeted for the SUSY2012 conference in August.
Update: Resonaances has more here, including the news that CMS will report 2012 data about the H->WW->lvlv channel (about the significance of this, see the June 29 posting at viXra log), and possibly others. Whether the 5 sigma significance level will be reached by a single experiment remains unclear…
Update: Finally confirmation from a reliable media outlet… The Daily Mail reports God particle is ‘found’. One evidence for this is that supposedly “Five leading theoretical physicists have been invited to the event on Wednesday”. This may mean Englert, Higgs, Guralnik, Kibble and Hagen, with Anderson getting dissed as usual.
Update: Tommaso Dorigo is providing background to the imminent Tevatron announcement here, and I assume will be discussing the actual results immediately upon release. The papers with the results will be released here this morning.
Update: The interesting bottom line from the Tevatron is that they see an excess in the bb channel that the LHC is not sensitive to, of size 2 +/- .7 times that predicted by the SM for a Higgs of mass 125 GeV. So, a marginally significant signal, of size consistent with the SM. The LHC should soon report the sizes of such signals in 3 other channels. In a couple of days we’ll have excesses in four channels, of sizes enough to claim discovery of a Higgs (or something very much like it, depending on how consistent the signal sizes are with the SM).
Update: The Tevatron paper on the Higgs combination is here. Most important number is the fit for the signal size for H->bb, for a 125 GeV Higgs. It’s 1.97 +.74/-.68 (where the SM prediction is 1).
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