Tuesday, 3 July 2012

Professor Higgs, your boson is ready

As has already been discussed extensively by many bloggers (including Jester, Tommaso, Shaun, and especially Peter Woit), CERN are holding a special seminar and press conference tomorrow morning, to announce the latest results on the hunt for the Higgs boson. It is widely rumoured that the evidence of a $\sim 125$ GeV Higgs from last year has strengthened to the point of being conclusive.

The plausibility of said rumours was only increased by a press release, which came out yesterday, giving the final results from the Higgs search at the Tevatron; the paper itself is available here. Presumably this has been rushed out before the CERN announcement, after which it would have been somewhat redundant. Anyway, both CDF and DZero saw a significant excess of Higgs-like events in the 115–140 GeV range; their mass resolution is not very good, and this is what might be expected with a Higgs mass in the 120's. The overall significance of the signal is reported as 2.9$\sigma$, including the look-elsewhere effect.

So it seems that the discovery of the last component of the standard model, which is now decades old, will be announced tomorrow morning. This is true regardless of whether CERN officially call this a discovery (they are not yet combining the results from ATLAS and CMS, but if the rumours are true, it will be perfectly clear that any reasonable such combination would comfortably surpass the conventional 5$\sigma$ required to use the word "discovery"). In a sense, then, this will be the final step in a long journey.

This is all very exciting, of course, but what will be interesting to see is whether the signal in various channels is compatible with the predictions of a vanilla standard model Higgs. For example, last year's data showed a small enhancement in the di-photon channel over what the standard model predicts, but obviously this wasn't yet very significant. I'm sure I will not be alone in hoping that the particle behaves at least slightly differently to the standard model Higgs, as this will give us hope that there is more to be discovered at the LHC (of course, there have already been vague hints from the flavour sector). We will see.

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