This is just coming in from the CERN conference in Geneva – the Higgs Boson has been noticed at the mass range 125-126 GeV with a HUGE confidence level of 4.9-sigma. Remember that the threshold is 5-sigma! That’s the BIG NEWS from the high energy world today.
Huge news: If you consider the Z-channel combined with the photon channel, we get 5-sigma! Higgs Discovery!
It’s nice to be at 5-sigma – CERN Spokesperson
But do note that this is just two channels. The Higgs has still not been officially discovered!
The World wide community
The CERN DG, Rolf Heuer, opened the Geneva conference and it was live webcasted to the ICHEP 2012 conference all the way in Melbourne, Australia. “Physics is a global community”, said Heuer. Many people were relieved that the presentation by CMS wasn’t in Comic Sans like last time! ATLAS stuck to Comic Sans though, much to everyone’s annoyance.
Higgs Status – the Bottomline
So this is what the scene looks like right now: There is a “significant excess” at 125 GeV and this is known with a 4.9-sigma confidence level. This means that there is a bump at 125 GeV, which cannot be ignored and this is known with 99.9997% certainty.
Results from CMS: Higgs Discovered
The mass range not excluded lies between 115 – 130 GeV. This rules out the minimal Standard Model Higgs expected at 141 GeV. The data collected in 2012 is about 5.2 fb-1. The mysterious comment comes through:
We are in a position to exclude the standard model
And then there was another one just as cryptic if not more:
What you will see today is existence of a new particle but you will not know its name
One of the most important channels for the low mass Higgs is the diphoton channel, or the Higgs decaying into two gamma ray photons. Here is a nice simulated picture that CMS gave out :
The double blind analysis by CMS led to the coincidence of the Look Elsewhere effect dips coming in at the same energy for both the 7 TeV and 8 TeV beams – at 125 GeV. Here is a screenshot:
The Higgs seen at 125.5 GeV is at 3.8 sigma confidence level for the 4-lepton channel. The same channel leads to a 3.2 confidence level with the look elsewhere effect taken into account.
The Z-boson and photon channel integrated gives 5 sigma!
The W-channel gives 1.5 sigma!
Bottomline: New Boson at 125.3 +/- 0.6 GeV at 4.9 sigma confidence level! That’s good enough for a discovery!
Results from ATLAS: Higgs Discovered
The number of events for the ATLAS collaboration is greater than for the CMS collaboration at 6.2 fb-1.
The excess has been noted in both the Z-channel and the photon channel. The confidence level is 3-sigma for the diphoton channel.
The 4-muon candidate mass converges on 125 GeV, bang on the value given by the CMS collaboration.
The excluded region’s lower limit is 130 GeV. The mass blackout is EVERYWHERE except between 122.6 and 129.7 GeV, with the exclusion happening at 99% confidence.
Huge applause as ATLAS mimics CMS results. The ZZ and diphoton channel combines to give 5.1 sigma confidence level for the existence of the Higgs Boson!
Here is the key slide for the ATLAS data:
We need more data. We are entering the era of Higgs measurements.
Bottomline: Higgs at 126.5 GeV at 5-sigma confidence level. No error is quoted.
Implication of a 125 GeV Higgs
The most immediate conclusion to draw from this is that there has to be something beyond the Standard Model. The minimalist models of the Standard Model predict that the Higgs mass ought to be at about 141 GeV. So a 125 GeV model is clearly a problem and leads to many problems like an unstable vacuum at energies much lower than the Planck scale. Supersymmetric models are our best bet in this situation.