MELBOURNE: High energy physics experiments at CERN have observed a new particle, consistent with Higgs boson, but with hints it might be something exotic, beyond the Standard Model of physics.
In a two-hour presentation, the spokespeople from two CERN experiments – the ATLAS detector and the CMS detector – presented their results to a packed auditorium at CERN, in Geneva, Switzerland, that was linked live with the 36th International Conference on High Energy Physics, being held in Melbourne, Australia.
Both experiments announced an observation of a new particle, in the mass range of 125-126 GeV, to thundering applause from both cities.
“It’s the heaviest ever found”
“This is indeed a new particle. We know it must be a boson and it’s the heaviest ever found,” said Joe Incandela, the spokesman for the CMS (Compact Muon Spectrometer) experiment.
“We have a discovery. We have a discovery of a new particle,” concluded Rolf Heuer, the Director General of CERN (European Organisation for Nuclear Research). “[The new particle] is consistent with a Higgs boson … but which one?” he asks.
The physicists are not sure if it is the Higgs boson predicted by the Standard Model of physics, which describes all the fundamental particles of matter.
Is it something more exotic?
“Are its properties as expected for the long-sought Higgs boson, the final missing ingredient in the Standard Model of physics? Or is it something more exotic?” the CERN press statement asks.
The Higgs boson is the final piece of the Standard Model, the answer to the question of why particles have different masses.
If it is more exotic than the Standard Model predicts, then new evidence will come from how the particle decays.
The boson is a very short-lived particle, and the ATLAS and CMS detectors can only measure what the Higgs boson decays into. In the mass ranges they looked at, there are five ways the Higgs boson can decay, producing: two Z bosons; two photons; two b quarks; two tau leptons; or two W bosons.
“The most important decay is the two photon decay, where both ATLAS and CMS have seen more of this decay than the Standard Model predicts,” said Christopher Hill from Ohio State University, and the deputy physics co-ordinator for CMS detector.
“If this trend continues as we add more data this year, this would be not just a discovery of the Higgs boson, but a discovery of some new physics,” he said.
“It’s hard not to get excited by these results,” said CERN research director Sergio Bertolucci. “We stated last year that in 2012 we would either find a new Higgs-like particle or exclude the existence of the Standard Model Higgs.
“With all the necessary caution, it looks to me that we are at a branching point: the observation of this new particle indicates the path for the future towards a more detailed understanding of what we’re seeing in the data.”
“We are entering the era of Higgs measurements,” said Fabiola Gianotti, the spokeswoman for the ATLAS experiment. “We need more data!”