(Reuters) - Scientists at Europe's CERN research centre 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.
For some, there was no doubt the Higgs boson is found: "It's the Higgs," said Jim Al-Khalili of Surrey University, a British physicist and popular broadcaster. "The announcement from CERN is even more definitive and clear-cut than most of us expected."
Higgs, now 83, from Edinburgh University was among six theorists who in the early 1960s 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.
He and some of the 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."
END OF AN ERA
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 which includes the photon, associated with light. The class is named in honor of 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."
Surrey's Al-Khalili said the researchers' caution was extreme: "Cutting through all the jargon about sigmas and decay channels, the bottom line is that CERN have indeed discovered the Higgs boson," he said. "In my view, if it looks like the Higgs, smells like the Higgs and is exactly what we expected from the Higgs, then it's the Higgs. Nobel prizes all round."
The Higgs theory explains how particles clumped together to form stars, planets and life itself. Without the Higgs boson, 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 exactly described by the Standard Model. It could 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, even more 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 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."
Jerome Gauntlett, head of theoretical physics at London's Imperial College said further experiments at CERN could begin to lighten the unexplained "dark matter" which theoreticians hold makes up much of the universe, explore a fourth dimension and beyond and resolve contradictions between the subatomic world of particles and the larger universe described by Einstein.
Reflecting on the scale of human endeavor to find the new particle, Joe Incandela, a spokesman for one of the CERN teams said: "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."
Paul Nurse, president of Britain's science academy The Royal Society, said: "This is a big day for science and for human achievement ... Today moves us a step closer to a fuller understanding of the very stuff of which the universe is made."
Higgs himself 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.
Without it, his ideas would remain just a paper theory and he conceded that he personally was never cut out for laboratory experimentation: "I certainly did some lab work as a schoolboy in Bristol," he told Reuters. "I was incompetent."