Beyond Higgs, CERN searches for unseen particle world
* Research looks to support a "theory of everything"
* Some voices of dissent over effort
* Discovery would back up string theory
By Robert Evans
GENEVA, Aug 8 (Reuters) - Scientists who stunned the world with their discovery of a particle that may be the basic building block of the universe now are on the lookout for a hitherto unseen world of particles that could open the way to finalising a "theory of everything."
CERN scientists, who announced last month that - almost certainly - the elusive Higgs boson had been spotted, are trawling through the vast volume of material produced in the Geneva research centre's Large Hadron Collider (LHC) for signs of what they call "SUSY".
Formally known as Supersymmetry, SUSY is the idea that every one of the elementary particles that make up the universe and everything in it has an almost, but not quite identical, "superpartner".
"SUSY is still a very valid option and we have just started to constrain it on the energy scale," CERN particle physicist Oliver Buchmueller told Reuters.
"There are many regions on the map of where it should be that we have still to explore."
Its existence, many researchers say, was supported by the presumed discovery of the Higgs with which, physicists say, it is inextricably linked.
"Supersymmetry," leading U.S. theoretician Matt Strassler says, "is a conjectured symmetry of space and time." It could be integrated with Albert Einstein's theory of relativity to provide a fuller explanation of the laws of nature.
Physicists say SUSY may explain the invisible dark matter that makes up around 80 percent of the solid substance of the universe, and would provide backing for "string theory" -- a leading contender for a "theory of everything".
String theory holds that instead of particles, the universe is composed of microscopic strings.
That overarching view would replace the present explanation of how the universe works -- the Standard Model, which was developed in the 1970s but has glaring gaps, including where gravity fits into the picture.
Searching for SUSY - or proving it a chimera - was always part of the programme for the subterranean LHC, in which particles are smashed together at near light-speed to create billions of explosions like the primeval Big Bang.
CERN director-general Rolf Heuer regularly includes it as one of the "New Physics" goals for the LHC. But some advance predictions before the giant machine began operations in March 2010 suggested SUSY signals could turn up quickly.
The fact that this has not proven to be the case has led to speculation in parts of the scientific media and blogosphere, as well as among some older researchers, that SUSY-hunting is taking particle physics up a blind alley.
"Is Supersymmetry dead?" asked a headline in the respected journal Scientific American in April this year. Writers on science websites have taken up the theme, suggesting that SUSY had better appear soon or it would indeed be defunct.
CERN's Buchmueller, who works on one of the LHC's two largest experiments, the CMS, and his colleague on the alternative ATLAS, Paul de Jong, strongly disagree.
"There is no scientific basis for that claim," said the German researcher, who shares time between Geneva and teaching at London's Imperial College of Science and Technology. "The theory is still very much alive."
"Supersymmetry is one of the most compelling possible extensions of the Standard Model and a leading contender for a new principle of nature than can be discovered in high-energy colliders," the pair said in a recent joint paper.
Other physicists at CERN and in research centres around the world argue that supersymmetrical particles are more likely to be spotted from early 2015 when the power of the LHC and the impact of its particle collisions will have been doubled.
"This was always going to be a long haul," Buchmueller said. (Reported by Robert Evans; Editing by Michael Roddy)
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