Higgs Boson and confidence levels

[SeventhSigma]

What is the current state of things? Are they fairly confident that the Higgs exist despite more data being needed for the 5-sigma confidence level? Could it still (realistically) turn out to not exist?

 

[kurros]

It could still turn out not to exist, yes, but it is not very likely in my opinion. They are seeing signals (albeit very small) in multiple search channels in multiple detectors in the same place. It would be a pretty large coincidence for this to occur under the background-only model, or a really unfortunate and strange screwup in the background modelling.

It may turn out to not quite have the correct properties for a Standard Model Higgs, in fact there is already minor evidence that some of the branching ratios are not quite right (but this could easily go away with more data). So I don't know if I would bet on it being exactly Standard Model like, but it seems close, and I would stick my money on them having something rather than nothing.

 

[mfb]

or a really unfortunate and strange screwup in the background modelling.

While this might be true for channels without direct mass measurements, the two-photon channel should not be affected by this. This plot from ATLAS shows some peak-like structure which is already visible by eye.

Are they fairly confident [...]

If you ask the scientists directly involved in the seach, they will tell you something about "it is too early to say this". But the usual opinion seems to be that this is the Higgs at ~125 GeV.