ATLAS and CMS experiments present Higgs search status

14 Dec 2011

In a seminar held at CERN yesterday, the ATLAS and CMS experiments presented the status of their searches for the Standard Model Higgs Boson.

Their results are based on the analysis of considerably more data than those presented at the summer conferences, sufficient to make significant progress in the search for the Higgs Boson, but not enough to make any conclusive statement on the existence or non-existence of the elusive Higgs.

The main conclusion is that the Standard Model Higgs Boson, if it exists, is most likely to have a mass in the range 115-130 GeV. Tantalising hints have been seen by both experiments in the same mass region, but these are not yet strong enough to claim a discovery.

Higgs Bbosons, if they exist, are very short lived and can decay in many different ways. Discovery relies on observing the particles they decay into rather than the Higgs itself. Both ATLAS and CMS have analysed several decay channels, and the experiments see small excesses in the low mass region that has not yet been excluded.

Taken individually, none of these excesses is any more statistically significant than rolling a die and coming up with two sixes in a row. What is interesting is that there are multiple independent measurements pointing to the region of 124 to 126 GeV. It's far too early to say whether ATLAS and CMS have discovered the Higgs Boson, but these updated results are generating a lot of interest in the particle physics community.

''We have restricted the most likely mass region for the Higgs Boson to 115-130 GeV, and over the last few weeks we have started to see an intriguing excess of events in the mass range around 125 GeV,'' explained ATLAS experiment spokesperson Fabiola Gianotti. ''This excess may be due to a fluctuation, but it could also be something more interesting. We cannot conclude anything at this stage. We need more study and more data. Given the outstanding performance of the LHC this year, we will not need to wait long for enough data and can look forward to resolving this puzzle in 2012.''