Physicists are more than 99 percent sure that they've found a new elementary particle that is likely the long-sought Higgs boson.

Evidence for the new particle was reported today (July 4) by scientists from the world's largest atom smasher, the Large Hadron Collider in Switzerland. Researchers reported they'd seen a particle weighing roughly 125 times the mass of the proton, with a level of certainty that all but seals the deal it's the Higgs boson.

"This is indeed a new particle. We know it must be a boson and it’s the heaviest boson ever found," Joe Incandela, spokesperson for LHC's CMS experiment, said in a statement. "The implications are very significant and it is precisely for this reason that we must be extremely diligent in all of our studies and cross-checks."

The Higgs, nicknamed the "God particle" (to the chagrin of many scientists, who prefer its official name), is thought to hold the key to one of the mysteries of the universe: Why do things have mass?

Its discovery represents a major step forward in our understanding of why the universe exists as it does, with matter clumping together to form galaxies, stars, planets and us, scientists say. [Top 5 Implications of Finding the Higgs Boson]

To be absolutely sure they've made a true new discovery, rather than simply seen a fluke, physicists wait for enough data so that their statistics reach a level called 5 sigma, meaning that there is only a one in 3.5 million chance the signal isn't real.

"We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV," said Fabiola Gianotti, spokesperson of LHC's ATLAS experiment. (GeV stands for gigaelecton volts, a unit of mass roughly equivalent to the weight of a proton.) Gianotti presented the findings to loud applause from physicists gathered at CERN (LHC's home facility) to hear the LHC's results.

The LHC's CMS experiment saw signs of a new particle with a mass of 125.3 GeV at a certainty level of 4.9 sigma.

"As a layman I would now say, I think we have it," CERN director general Rolf Heuer said during a presentation at the Geneva, Switzerland lab reporting the results today. "Do you agree?" he asked the gathered physicists, who responded with loud applause.

The Higgs boson is the last undiscovered piece of the puzzle predicted by the reigning theory of particle physics, called the Standard Model. Yet the model does not predict what its mass is, so physicists have to search through a wide territory to find it. The researchers can't yet be absolutely sure that the new particle they've found actually is the Higgs.

"The work now is to actually measure its quantum identity (all its quantum properties)," Caltech physicist Maria Spiropulu, who was in the audience at the LHC announcement, told LiveScience in an email. "Then we can say if it THE minimal standard model Higgs or a Higgs look-alike. We have been propelled to the future of particle physics towards the understanding of the fundamental properties of our universe in its entirety."

The LHC is the most powerful machine on Earth, capable of smashing protons together to produce huge explosions of energy that transform into new and exotic particles inside its17-mile (27 kilometer) underground loop. Yet the Higgs boson is so rare only one out of a trillion of the collisions inside the accelerator are likely to produce it, and even then, it decays almost immediately into other particles.

"This is not a needle in a haystack — it's much worse than a needle in a haystack," said Joe Lykken, a theoretical physicist at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill.

Over the past few years, researchers have been able to exclude certain possible masses for the Higgs, narrowing the possible window for Higgs further and further. Just this week, Fermi scientists announced that data from the largest U.S. particle accelerator, the Tevatron (which shut down last year), show the Higgs, if it exists at all, must have a mass between 115 and 135 GeV.

In December 2011, the LHC teams announced their latest findings, which restricted the Higgs to a mass between115 and 130 GeV, though with less certainty than the new Tevatron results.

"This is a really special time," said Fermilab physicist Dan Green, a member of LHC's CMS experiment, said Monday (July 2). "I remember when the top [quark] was discovered 20 years ago. This is one of the most exciting weeks I've had for a very long time." [9 Unsolved Physics Mysteries]

Today's findings come from the two general-purpose experiments at LHC, ATLAS and CMS. Both observed particle collisions independently and analyzed their observations separately. In fact, scientists from each team were not allowed to tell each other what they found until today, for fear their results would bias the other experiment's researchers toward looking for the same results.

GENEVA (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."

UNIVERSAL THEORY

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.

EXPLORATION AHEAD

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."

Renowned British physicist Stephen Hawking said Wednesday the Nobel Prize should be given to Peter Higgs, the man who gave his name to the Higgs boson particle.

Former Cambridge University professor Hawking also joked that the discovery had actually cost him $100 in a bet.

In an interview with the BBC Wednesday, Hawking, who has motor neurone disease, said: "This is an important result and should earn Peter Higgs the Nobel Prize.

"But it is a pity in a way because the great advances in physics have come from experiments that gave results we didn't expect.

"For this reason I had a bet with Gordon Kane of Michigan University that the Higgs particle wouldn't be found. It seems I have just lost $100."

After half a century of research, physicists announced at the European Organisation for Nuclear Research (CERN) Wednesday they had found a new sub-atomic particle consistent with the elusive Higgs boson which is believed to confer mass.

Hawking said the discovery was of major importance.

"If the decay and other interactions of this particle are as we expect, it will be strong evidence for the so-called standard model of particle physics, the theory that expains all our experiments so far," Hawking said.

GENEVA (Reuters) - Peter Higgs was no good in the lab, but he never doubted that one day his theory of a powerful subatomic particle that bears his name would be proven right in practice. His surprise was that he lived to see that day.

Speaking at Geneva's CERN research center on Wednesday after its experimental physicists announced the discovery of a new particle, a boson much as Higgs imagined half a century ago, he confessed to Reuters he felt "rather dazed but very pleased."

As a schoolboy in Bristol in the southwest of England, the now 83-year-old Higgs admitted to being "incompetent" at science in the laboratory. He went on, however, to specialize in the theoretical realm, applying mathematics to exploring the outer reaches of man's understanding of the universe that makes us.

One paper he dispatched from Edinburgh University in 1964, as he was formulating a theory of an elusive particle to explain how an ordered universe emerged from Big Bang, was rejected by an academic physics journal edited at CERN.

But he gave no sign of bearing a grudge when he spent Wednesday at the institution watching its experimental experts vindicate him: "For me personally it is just the confirmation of something I did 48 years ago, and it is very satisfying to be proved right in some way," Higgs said in the interview.

"I haven't been dreaming about it for 48 years because I had other things to do with my life. At the beginning, I had no expectation that I would still be alive when it happened."

That experimental proof had been delivered in his own lifetime was, he said, "incredible" and he suggested the moment would have greatly surprised his early science teachers: "I certainly did some lab work as a schoolboy in Bristol. I was incompetent," he said, a boyish grin flitting across his round face.

For nearly three decades, physicists at CERN and the U.S. Fermilab research centers had tried to find what had become known as the "Higgs boson" in particle colliders creating mini-explosions duplicating the Big Bang of 13.7 billion years ago.

And although CERN hedged its bets in their report on Wednesday, and held back on claiming it had discovered the Higgs until they had time to "get inside" it, they were sure they had found a new particle.

NO SCHADENFREUDE

The rotund, bespectacled theoretical physicist who for many years held a professorial chair at Edinburgh University, gave no hint of schadenfreude over the fact that his original idea was rejected by a CERN journal as "of no relevance to physics."

"What I did 48 years ago wasn't very specific," he said. Earlier, at a news conference, he had refused to get into what his feelings were. "This day belongs to CERN and the people who work here," he insisted.

Higgs, who has strong views on what is good and bad about science and resigned from a movement for nuclear disarmament when it began campaigning against the harnessing of nuclear energy, makes clear he has no religious faith.

He said he was not worried by the fact that it was not yet finally established whether the new boson -- sometimes dubbed, to his disgust and that of all CERN scientists, "the God particle" -- was exactly as he conceived it.

His vision of a particle linked to a force field that attracted the flying debris of the Big Bang and turned it into stars, planets, and galaxies "was about a type of theory and I'm not particularly bothered if this is a single Higgs boson or one of several," he told Reuters.

But, he added, it would be "rather surprising" if study of the new boson over coming months in CERN's Large Hadron Collider (LHC) showed "deviations from the expectations for the properties of any kind of Higgs boson."

CERN experts say that if such a scenario -- discovery that the new boson was something totally outside their expectations -- were to unfold, the whole modern concept of how the universe works would have to be reviewed.

The Higgs, in its basic form, has long been seen as filling in the last major gap in the so-called Standard Model of physics -- drawn up in the 1970s -- describing the way the universe works at the most elementary level.

"From the point of view of future physics," said the scientist -- who has two sons, a computer engineer and a jazz musician -- "It seems to me that in one way it is the end of an era in that it appears to complete the Standard Model.

"But the more important thing is that studying it (the new particle) will lead onto what lies beyond that model which we hope will have more interesting connections with cosmology, the dark matter problem, and that sort of thing."

SCIENCE FICTION

CERN physicists say the finding of the boson -- widely hailed as the biggest advance in knowledge about the cosmos for over 30 years -- will open the door to probing this and other ideas that were once the stuff of science fiction.

Gravity remains unexplained outside the model, although it is the force that created the black holes at the center of galaxies and elsewhere in the universe, which suck in anything that comes close to them.

Other concepts which scientists say could now be examined more closely are super-symmetry, the idea that all particles have a much heavier counterpart, the "dark matter" believed to make up about 23 percent of the universe but cannot be seen, and "dark energy" that constitutes about 72 percent.

"You may call it science fiction, but to me these are speculative theories which have been around for quite some time, and it's only now they are beginning to be tested," said Higgs.

"As with the Higgs boson, there's a lot of theoretical motivation for some parts of these theories to be true, in particular super-symmetry, which I think most people would say is a necessary feature of any theory that is going to unify the Standard Model with gravity.

"If we don't unify these theories with gravity, there is something very funny going on because gravity on its own doesn't fit in properly with quantum theory" -- the over-riding theory of the nature of matter which evolved in the first half of the 20th century.