By Robert Evans
GENEVA (Reuters) - U.S.-based physicists said on Monday they hope to have enough data by the end of this month to establish if the elusive Higgs boson, a particle thought to have made the universe possible, exists in its long-predicted form.
If the answer is no, scientists around the globe will have to rethink the 40-year-old Standard Model of particle physics which describes how they believe the cosmos works.
The physicists, at the Fermilab research center near Chicago which operates the Tevatron collider, have been in friendly competition with colleagues at CERN near Geneva whose giant LHC machine is also seeking the Higgs.
In an e-mail to Reuters in Geneva, Fermilab communications director Katie Yurkewicz said Tevatron was on track to have by September 30 the information "to rule out the existence of a Higgs boson with a mass within the most likely range."
Both Tevatron, operating for the past 28 years, and CERN's Large Hadron Collider, started up on March 30 2010, have been trying to find the boson -- postulated as the particle that gave mass to matter after the Big Bang 13.7 billion years ago -- within that range.
If it is not there, scientists say, then the multi-national research teams at both centres will have to start looking in the data gathered and more to come for something else -- a different sort of Higgs or some other particle.
But if it is somewhere there, Yurkewicz and her Fermilab colleague Robert Roser say, the Tevatron would not have enough data to confirm its existence before September 30 -- when the U.S. collider, denied necessary funds, closes down for good.
MULTIPLE SIGHTINGS NEEDED
Scientists at both centres say there will have to be multiple sightings of the Higgs -- each of which will have to be minutely scrutinized to ensure they are what they appear to be -- before a discovery can be announced.
Reaching the conclusion that it is not where it should be is much easier.
In the two machines -- the LHC oval-shaped and the Tevatron circular but smaller -- particles are smashed together at near the speed of light, recreating the primal chaos of flying matter a tiny fraction of a second after the Big Bang.
The result of those collisions -- and there have been trillions of them -- are recorded on computer disc and studied by scientists around the world for any trace of the Higgs, a key element of the Standard Model, and of any new phenomena.
Scientists at CERN, formally the European Organization for Nuclear Research, have themselves been gathering data from collisions at an ever-growing rate but have yet to spot more than a fleeting hint that it might exist.
"The Higgs boson has been rather elusive so far and no-one really knows what it will look like," wrote CERN scientist Paulime Gagnon in her blog on Monday.
"But if it exists, and if it is the one predicted by the Standard Model, then we know how to set traps to catch some."
CERN's director-general Rolf Heuer has said he expects proof one way or another to emerge in 2012, at the end of which the $10 billion LHC will shut down for a year to be prepared for collisions at twice the present force.
But some CERN researchers have suggested that the vast amount of data they are collecting could allow them to come to at least a preliminary conclusion -- Higgs or no Higgs -- by the end of this year.
(Reported by Robert Evans; Editing by Andrew Heavens)