Geneva - Cern scientists reporting from the Large Hadron Collider (LHC) have claimed the discovery of a new particle consistent with the Higgs boson. The particle has been the subject of a 45-year hunt to explain how matter attains its mass.
The results announced at Cern, home of the LHC in Geneva, were met with loud applause and cheering.
Peter Higgs, after whom the particle is named, wiped a tear from his eye as the teams finished their presentations in the Cern auditorium.
"I would like to add my congratulations to everyone involved in this achievement," he added later.
"It's really an incredible thing that it's happened in my lifetime."
Both of the Higgs boson-hunting experiments at the LHC see a level of certainty in their data worthy of a "discovery". More work will be needed to be certain that what they see is a Higgs, however.
The CMS team claimed they had seen a "bump" in their data corresponding to a particle weighing in at 125.3 gigaelectronvolts (GeV) - about 133 times heavier than the proton at the heart of every atom.
They claimed that by combining two data sets, they had attained a confidence level just at the "five-sigma" point - about a one-in-3.5 million chance that the signal they see would appear if there were no Higgs particle.
However, a full combination of the CMS data brings that number just back to 4.9 sigma - a one-in-2 million chance.
Joe Incandela, spokesman for CMS, was unequivocal: "The results are preliminary but the five-sigma signal at around 125 GeV we're seeing is dramatic. This is indeed a new particle," he told the Geneva meeting.
Rolf Heuer, director-general of Cern, commented: "As a layman I would now say I think we have it."
"We have a discovery - we have observed a new particle consistent with a Higgs boson. But which one? That remains open.
"It is a historic milestone but it is only the beginning."
A confirmation that this is the Higgs boson would be one of the biggest scientific discoveries of the century; the hunt for the Higgs has been compared by some physicists to the Apollo programme that reached the Moon in the 1960s.

Process of a 'discovery'

•    Particle physics has an accepted definition for a discovery: a "five-sigma" (or five standard-deviation) level of certainty
•    The number of sigmas measures how unlikely it is to get a certain experimental result as a matter of chance rather than due to 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
•    A "three-sigma" level represents about the same likelihood as tossing eight heads in a row
•    Five sigma, on the other hand, would correspond to tossing more than 20 in a row
•    Independent confirmation by other experiments turns five-sigma findings into accepted discoveries