Scientists at Cern, the European physics research centre, expect to reveal on Tuesday that they are tantalisingly close to detecting the Higgs boson, sometimes known as the “God particle”.
This subatomic particle, which is seen as playing a fundamental role in the workings of the universe, is target number one for researchers working with the world’s most powerful atom smasher, the Large Hadron Collider.
Rumours about the discovery of the Higgs particle have swirled around Cern headquarters in Geneva from time to time since the LHC began gathering data in earnest early this year – and disappeared on further investigation.
The mood is more confident now, ahead of Tuesday’s seminar when the findings from the LHC’s two main experiments – involving a vast amount of data about collisions between hydrogen nuclei at close to the speed of light – are reported. These collisions generate microscopic fireballs of intense energy from which new particles form, hopefully including Higgs.
“We won’t know until the last minute how far we can go with a statement at the seminar because data are still being analysed,” said a Cern insider.
Officially the organisation is just saying that the results will be “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 Higgs.”
Higgs is the last element of the theory known as the “standard model” of particle physics whose existence has still to be confirmed. Its role in the theory, which dates back to the 1960s, is to give mass to other particles, in a way that can only be explained through complex quantum mechanics. In oversimplified terms, mass results from particles bumping into “virtual” Higgs bosons that are constantly appearing and disappearing in empty space.
If Higgs turned out not to exist, it would leave a huge hole in the heart of physics theory. This might excite some theorists but it would be a public relations challenge for Cern, which raised $8bn from the world’s governments to build the LHC partly on the promise of discovering Higgs.
Physicists point out that discovering a particle at an atom smasher is not a eureka moment when they suddenly see something exciting in the debris from a collision. Rather it results from the painstaking computer analysis of vast volumes of data by hundreds of scientists, looking for patterns indicative of a new particle.
The Higgs itself not only bestows mass on other particles but also has its own mass. One obstacle to finding it has been that theorists cannot predict with any certainty what this mass might be.
According to the latest rumours, analysis suggests that Higgs has a mass about 125 times greater than a proton or neutron.
Cern will not be able to claim officially that Higgs has been discovered because, according to the conventions of physics, a new particle requires “5-sigma” statistical confidence – which means there is less than a one-in-a-million chance of its being wrong. At best, the latest analysis is likely to give 3-sigma confidence.