Scientists may be closing in on the most sought-after particle in physics.
The hypothetical Higgs boson, often dubbed the "God particle", is fundamental to our understanding of the Universe but has yet to be detected.
Now, data from the Tevatron particle collider at Fermilab, in the US, has enabled the most precise calculation yet to be made for its predicted mass.
And this, the international team says, narrows the window in which to locate the elusive particle.
The Higgs boson has been proffered to explain the mystery of why other particles have mass, and forms the missing piece in the puzzle that is the Standard Model - the current theory used to describe the fundamental nature of matter.
For years, researchers have been searching the sub-atomic "soup" created when particles are smashed together in colliders - but no sign of the Higgs has been seen.
In obtaining a more precise predicted mass for the Higgs, the particle's existence can be confirmed or ruled out within two to three years, scientists believe.
The calculation has been done by making the finest measurement to date of the mass of another elementary particle, one that is well known, the W boson.
The W boson is the carrier of weak nuclear force, one of the fundamental forces in nature, and its mass is believed to be linked to that of the Higgs'.
Using this new measurement, together with the calculated mass of another fundamental particle, the top quark, the Fermilab team has worked out a new predicted mass for the Higgs boson, discovering it might be lighter than previously thought.
Dr Mark Lancaster, UK spokesman for the Collider Detector at Fermilab (CDF), from University College London, said: "These findings narrow down the mass region that we expect the Higgs to appear in.
"After more than 10 years, we are now homing in on it."
And searching data within this region at Fermilab's Tevatron and Europe's Large Hadron Collider at Cern, which switches on next year, could reveal whether the Higgs boson is present or not by the middle of 2009, he added.
"And if we don't find it, it is going to be back to the drawing board for particle physics."
The Standard Model is a theory devised to explain how sub-atomic particles interact with each other
There are 16 particles that make up this model (12 matter particles and 4 force carrier particles). But they would have no mass if considered alone
The Higgs boson explains why these particles have mass. Particles acquire their mass through interactions with an all-pervading field, called the Higgs field, which is carried by the Higgs boson.