(Reuters) - Scientists at Europe's CERN research center have found a new subatomic particle, a basic building block of the universe, which appears to be the boson imagined and named half a century ago by theoretical physicist Peter Higgs.
"We have reached a milestone in our understanding of nature," CERN director general Rolf Heuer told a gathering of scientists and the world's media near Geneva on Wednesday.
"The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle's properties, and is likely to shed light on other mysteries of our universe."
Two independent studies of data produced by smashing proton particles together at CERN's Large Hadron Collider produced a convergent near-certainty on the existence of the new particle. It is unclear whether it is exactly the boson Higgs described.
But addressing scientists assembled in the CERN auditorium, Heuer posed them a question: "As a layman, I would say I think we have it. Would you agree?" A roar of applause said they did.
Higgs, now 83, from Edinburgh University was among six theorists who proposed the existence of a mechanism by which matter in the universe gained mass. Higgs himself argued that if there were an invisible field responsible for the process, it must be made up of particles. The particle is the emissary of the field and proves its existence.
He and others were at CERN to welcome news of what, to the embarrassment of many scientists, some commentators have labeled the "God particle" for its role in turning the Big Bang into a living universe: Clearly overwhelmed, his eyes welling up, Higgs told the symposium of fellow researchers: "It is an incredible thing that it has happened in my lifetime."
He later told Reuters of his admiration for the work of the thousands of scientists and engineers who worked on the practical experimental and statistical work which had, finally, confirmed what he and others had described with mathematics.
"I had no expectation that I would still be alive when it happened," he said of the speed with which they found evidence.
"It is very satisfying," he said. "For me personally it's just the confirmation of something I did 48 years ago."
He predicted further investigation by the CERN teams would probably confirm the particle is at least related to his idea: "It would be very odd if it were not any kind of Higgs boson."
"For physics, in one way, it is the end of an era in that it completes the Standard Model," he said of the basic theory physicists currently use to describe what they understand so far of a cosmos built from 12 fundamental particles and four forces.
The two separate teams at CERN worked independently through data, hunting for tiny divergences that might betray the existence of the new boson, a class of particle named for Albert Einstein's Indian collaborator Satyendra Nath Bose.
"It's a boson!" headlined Britain's Science and Technology Facilities Council in a statement on its researchers' role in the delivery of the "dramatic 5 sigma signal" for the existence of the long-sought particle.
Five sigma, a measure of probability reflecting a less than one in a million chance of a fluke in the data, is a widely accepted standard for scientists to accept the particle exists.
"The fact that both our teams have independently come to the same results is very powerful," Oliver Buchmueller, a senior physicist on one of the research teams, told Reuters.
"We know it is a new boson. But we still have to prove definitively that it is the one that Higgs predicted."
Bosons are one of two fundamental classes of subatomic particle. Other bosons include photons, associated with light.
The Higgs theory explains how particles clumped together to form stars, planets and life itself.
Without the Higgs particle, the universe would have remained a formless soup of particles shooting around at the speed of light, the theory goes.
It is the last undiscovered piece of the Standard Model that describes the fundamental make-up of the universe. The model is for physicists what the theory of evolution is for biologists.
What scientists do not yet know from the latest findings is whether the particle they have discovered is the Higgs boson as described by the Standard Model. It could also be a variant of the Higgs idea or an entirely new subatomic particle that could force a rethink on the fundamental structure of matter.
The last two possibilities are, in scientific terms, the most exciting.
Packed audiences of particle physicists, journalists, students and even politicians filled conference rooms in Geneva, London and a major physics conference in Melbourne, Australia, to hear the announcement.
Despite the excitement, physicists cautioned that there was still much to learn: "We have closed one chapter and opened another," said Peter Knight of Britain's Institute of Physics.
Buchmueller at CERN said: "If I were a betting man, I would bet that it is the Higgs. But we can't yet say that definitely yet. It is very much a smoking duck that walks and quacks like the Higgs. But we now have to open it up and look inside before we can say that it is indeed the Higgs."
CERN research director Sergio Bertolucci said: "It's hard not to get excited by these results.
"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."
Joe Incandela, a spokesman for one of the CERN research teams, said the new boson his team observed had a mass of 123.3 gigaelectron volts (GeV).
Reflecting on the scale of the endeavor to find it, he added: "It's been an incredible project over two decades. It has involved around 3,300 scientists to get to this result ... These results are now global and shared by the whole of mankind."
Higgs called it a great achievement for the Large Hadron Collider, the 27-km (17-mile) long particle accelerator built in a tunnel underneath the French-Swiss border where experiments to search for the Higgs boson have taken place.
Of his own scientific career, he conceded he had always been cut out for mathematical theorizing rather than experimental labors in the laboratory: "I certainly did some lab work as a schoolboy in Bristol," he told Reuters. "I was incompetent."