13 December 2011 Last updated at 12:44 ET

Analysis: Higgs result offers glimpse of the future

By Paul Rincon Science editor, BBC News website, Geneva

Finding the Higgs boson would be considered to be the one of the greatest discoveries of modern physics

After weeks of speculation, the wait is over.

While not definitive enough to claim a discovery, new results provide the best evidence yet for the existence of the elusive and coveted Higgs boson.

The heads of the two experiments that are searching for glimpses of the Higgs using the Large Hadron Collider (LHC) gave their talks in the auditorium at Cern - the organisation that operates the collider.

Finding the Higgs would be a huge discovery - on a par, according to some, with the discovery of DNA more than 60 years ago. But others think it would be in a class of its own. It is the cornerstone of the current theory of particle physics - which explains how particles and forces interact.

The Higgs boson

• The Higgs is a sub-atomic particle that is predicted to exist, but has not yet been seen
• It was proposed as a mechanism to explain mass by six physicists, including Peter Higgs, in 1964
• It imparts mass to other fundamental particles via the associated Higgs field
• It is the last missing member of the Standard Model, which explains how particles interact

• Higgs 'may have been identified'
• Q&A: The Higgs boson

But it would also confirm that scientists have been on the right track to understanding what makes the Universe tick.

Scientists have both narrowed the Higgs search range substantially and provide tantalising hints that something might - just might - be showing itself at the mass of 125 gigaelectronvolts (GeV).

"The window for the Higgs gets smaller and smaller. Yet it is still alive," said Prof Rolf Heuer, director-general of Cern.

Summing up the talks, he added: "Be prudent - we have not found it yet."

No room for feelings

Prof Heuer has been extremely cautious and less upbeat than some about the result.

Statistics of a 'discovery'

• Particle physics has an accepted definition for a "discovery": a five-sigma level of certainty
• The number of standard deviations, or sigmas, is a measure of how unlikely it is that an experimental result is simply down to chance rather than a real effect
• Similarly, tossing a coin and getting a number of heads in a row may just be chance, rather than a sign of a "loaded" coin
• The "three sigma" level represents about the same likelihood of tossing more than eight heads in a row
• Five sigma, on the other hand, would correspond to tossing more than 20 in a row
• Unlikely results can occur if several experiments are being carried out at once - equivalent to several people flipping coins at the same time
• With independent confirmation by other experiments, five-sigma findings become accepted discoveries

Asked earlier what he felt in his bones, Prof Heuer said that what he felt was immaterial: "Physics is not about feelings, it is about science and logic," he said.

It is perhaps understandable. If he said anything else it would make Cern look as if it had jumped the gun if these hints diminished - as many signals have done in the past.

The reasons for caution are also scientific. Five sigma is the level of statistical certainty required to claim a discovery. Three sigma can be counted as an observation. But, says Pippa Wells, a senior scientist on Atlas, "we are not even there yet".

The certainty of what the scientists have seen is not much higher than throwing one die and getting two sixes in a row - around the two sigma level.

But they are now analysing five times as much data as have been presented before. And the fact that both experiments see an "excess" or data spike at 125 gigaelectronvolts (GeV) is extremely tantalising.

It might even suggest the elusive boson may finally be emerging from the mist.

Sandra Koitner, a scientist on Atlas, agreed that the agreement between the two experiments boosted the probability of this being a real effect.

But she told BBC News: "He (Prof Heuer) is right to be cautious. But we are very excited to see some hints… we have been waiting years for this."

Now they have to collect more data to strengthen the statistical certainty what they are seeing is real.

Pippa Wells explained that by next year the LHC will have as much as four times as much data as they currently have.

That should close out the Higgs question once and for all.