Teams at the Large Hadron Collider, the €3bn atom-smashing machine near Geneva, say they have found a new subatomic particle “consistent” with the Higgs boson.
The results are preliminary and more work is needed before the scientists can be sure of what “species” of particle they have captured.
But observations carried out so far show it looks and acts like the particle that has eluded them for 50 years.
Finding the Higgs is vital to the Standard Model, the theory that describes the web of particles, forces, and interactions that make up the universe.
Without the Higgs boson to give matter mass there could be no Standard Model universe. If it was proved not to exist scientists would have to tear up the theory and go back to the drawing board.
Yesterday’s announcement came at a packed seminar at the Geneva headquarters of Cern, the European Organisation for Nuclear Research, where a tense audience heard the latest progress report from the Large Hadron Collider.
Speaking at a London briefing with a live link to the seminar, Professor John Womersley, chief executive of the Science and Technology Research Council, said: “They have discovered a particle consistent with the Higgs boson. Discovery is the important word; that is confirmed. It’s a momentous day for science.”
Last December, scientists at the Large Hadron Collider revealed they had caught the first tantalising glimpses of the particle.
But the process of proving a new piece of the universe is real is a slow and careful one, similar to getting closer to a familiar face seen from afar.
Since the initial excitement, the scientists have sifted through vast quantities of data from billions of high energy collisions in an effort to reduce the chances of being wrong.
Now they confirmed that two of the Large Hadron Collider’s giant detectors, CMS and Atlas, had delivered results that reached the definitive “five sigma” level of proof.
A sigma is a measure of how likely it is that a finding is down to chance. At five sigma, the likelihood of a statistical fluke is one in a million.
Professor Peter Higgs, the retired British physicist from Edinburgh University after whom the particle was named, was in the Geneva audience.
He later told 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.
Scientists say they have found a new subatomic particle which looks like the long-sought Higgs boson, which gives matter mass.
Q. What is the Higgs boson and the Higgs field?
The Higgs field has been described as a kind of cosmic “treacle” spread through the universe. As particles travel through the treacle they slow down, lose energy and get heavier. The Higgs boson is the force-carrying particle that helps transmit the effects of the Higgs field.
Q. How did it get its name?
Until recently, Professor Peter Higgs was as unknown to most of the world as the famous particle that bears his name. Today the quiet physicist, now retired from the University of Edinburgh, is fast becoming a global celebrity as creator of the theory behind the “God particle”.
Q. When did he make the discovery?
Prof Higgs, 83, has been waiting since 1964 for science to catch up with his ideas about the Higgs boson.
It was in that year he dreamed up the concept in a moment of inspiration while walking in the Cairngorms.
Prof Higgs’s groundbreaking proposal was that particles acquire mass by interacting with an all-pervading field spread throughout the universe. The more they interact, the more massive and heavy they become.
A “boson” particle was needed to carry and transmit the effect of the field — the Higgs boson.
Q. What would the world be like without the Higgs boson?
According to the Standard Model theory, it would not be recognisable. Without something to give mass to the basic building blocks of matter, everything would behave as light does, floating freely and not combining with other particles. Ordinary matter, as we know it, would not exist.
Q. How long has the search gone on?
Scientists have been looking for the Higgs since the 1960s, but the search began in earnest more than 20 years ago with early experiments at Cern in Europe and Fermilab in the US.
Q. How do you find a Higgs boson?
Protons are spun at almost the speed of light in opposite directions and smashed together. The enormous energy released is converted into matter in the form of new particles.
This is in keeping with Einstein’s famous equation E=mc², which shows that mass and energy are interchangeable. Like other heavy particles, the Higgs decays into lighter particles, which then decay into even lighter ones.
The process can follow a certain number of paths, which depend on the particle’s mass.
Physicists compare the decay paths they observe after a particle collision to predicted decay paths simulated with computers. When a match is found, it suggests that the observed particle is the one being searched for.