Scientists say they have found a new particle consistent with the long-sought "God particle''.
The physicists say they have discovered a particle consistent with the Higgs boson, a theoretical particle that is key to the scientific understanding of all matter.
The European Organisation for Nuclear Research or CERN said the discovery was a milestone in the understanding of nature.
Physicists stressed the results presented at a joint conference in Melbourne and Geneva were preliminary.
They were unsure if the particle was the long sought-after Higgs boson, or God particle, or something more "exotic''.
"The next step will be to determine the precise nature of the particle and its significance for our understanding of the universe,'' a CERN statement said.
CERN director general Rolf Heuer said it was a milestone.
"We have reached a milestone in our understanding of nature,'' he said.
"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.''
Physicists have been trying for 30 years to find evidence that the theoretical subatomic particle exists, leading to the CERN experiments using the $10 billion Large Hadron Collider particle accelerator, 100 metres underground near Geneva.
A summary of experiments conducted by one of the two teams at the Large Hadron Collider said further analysis of the particle was needed.
"More data are necessary to establish whether this new particle has all the properties of the SM Higgs boson or whether some do not match, implying physics beyond the standard model,'' a statement on the CMS results said.
A spokesman for the second team ATLAS, Fabiola Gianotti, said they observed clear signs of a new particle.
"More data and more study will be needed to determine the new particle's properties.''
The Higgs boson is the missing piece of the jigsaw puzzle, an Australian scientist said.
Professor Anthony Thomas, based at the University of Adelaide, said it was the most important and profound discovery in particle physics in almost 30 years.
"The Higgs represents the key missing piece of the jig-saw puzzle that is the famous standard model of nuclear and particle physics,'' Prof Thomas said.
"It has been anticipated for more than four decades and were it not there theorists all over the world would have been back to their drawing boards in desperation.''
CERN's atom smasher, the $10 billion Large Hadron Collider on the Swiss-French border, has been creating high-energy collisions of protons to investigate dark matter, antimatter and the creation of the universe, which many theorize occurred in a massive explosion known as the Big Bang.
The phrase "God particle," coined by Nobel Prize-winning physicist Leon Lederman, is used by laymen, not physicists, more as an explanation for how the subatomic universe works than how it all started.
Rob Roser, who leads the search for the Higgs boson at the Fermilab in Chicago, said: "Particle physicists have a very high standard for what it takes to be a discovery," and he thinks it is a hair's breadth away. Roser compared the results that scientists will announce Wednesday to finding the fossilized imprint of a dinosaur: "You see the footprints and the shadow of the object, but you don't actually see it."
THE HIGGS BOSON
What is the Higgs boson?
A theoretical sub-atomic particle that would be evidence of the theorised "Higgs field'', a force believed to give matter its mass.
What is a Higgs field?
In the 1960s, physicist Peter Higgs theorised the Higgs field permeates the universe and gives particles their mass.
What is the Large Hadron Collider?
A 27km tunnel in which beams of particles are smashed together at high speed. The results of the collisions have been analysed in the search for the sub-atomic Higgs boson.
Why are scientists looking for the Higgs boson?
The Higgs boson explains how matter gets its mass. The theory is key to scientists' understanding of particles. If the Higgs boson is proven to exist, that knowledge can be used to answer questions about other mysteries of the universe.
- with AAP