Scientists on Tuesday offered a tantalising glimpse of a subatomic fragment sometimes called the “God particle” because it gives substance to all matter in the universe.
But, in an atmosphere of fevered expectation, they stopped short of claiming to have discovered the Higgs boson particle, the existence of which half a century of physics theory depends on.
The scientists at Cern, the European physics research centre, presented the latest evidence for the existence of the Higgs boson from atom-smashing experiments at the $8bn Large Hadron Collider (LHC) near Geneva.
Their results were less clear-cut than some of the more enthusiastic speculation last week, which suggested that the Higgs had in effect been discovered – and some statistical tidying up was all that was needed to confirm it.
“Tantalising hints have been seen,” Cern’s summary of the results said, “but these are not strong enough to claim a discovery.”
“Be careful,” added Rolf Heuer, Cern director-general, who has spent the past year fighting premature rumours that his scientists have definitively detected the Higgs. “These are preliminary results – intriguing hints of the Higgs – but we have not found it yet.”
Even so physicists were bubbling with excitement after the presentation, which gave them the best glimpse so far. “The Cern results on the Higgs boson have the scientific world agog,” said Themis Bowcock, head of particle physics at the University of Liverpool.
The so-called Standard Model of physics, developed since the 1960s, relies on the Higgs boson, a subatomic particle that interacts with other particles to make some massive while leaving others light – and yet others entirely massless. This shapes the universe we know today.
Two giant detectors, known as Atlas and CMS, have been analysing the particles generated in billions of collisions between protons (hydrogen nuclei) travelling in opposite directions round the LHC’s underground ring at almost the speed of light.
Higgs bosons, if they exist, do not last long enough to show up directly in the subatomic debris of these collisions. Discovery relies on observing the particles into which Higgs bosons disintegrate, rather than detecting them directly. But the mass of the Higgs itself is unknown, leaving much uncertainty about the best place to look for decay particles.
Both Atlas and CMS have found small excesses of potential decay particles which would be consistent with a Higgs boson having a mass about 130 times greater than a proton or neutron.
“It is possible that each observation is simply a statistical fluke, a fluctuation in the background, mimicking a Higgs signal,” said Prof Bowcock. “But the fact that Atlas and CMS independently agree on the possible Higgs mass substantially increases the overall significance of the results.”
“We still need many more collisions next year on the Higgs to answer the Shakespeare question: to be or not to be?” concluded Prof Heuer.