Fri, Apr 06, 2007 page2

• Taiwanese, US physicists find evidence of X particle

  'GREATER SIGNIFICANCE' Even if the scientists did not discover a standard-model Higgs boson, their finding could expand the theoretical foundations of physics

  • STAFF WRITER
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  The existence of a "X particle" previously observed by a US laboratory was confirmed by a trio of Taiwanese and US researchers as one of the hypothetical Higgs bosons, academic sources reported on Wednesday.

  They said the discovery may not only subvert the long-held "standard model" in particle physics, but also make way for the discovery of dark matter.

  He Xiao-gang (何小剛) of National Taiwan University (NTU), Jusak Tandean of University of La Verne and G. Valencia of Iowa State University published their findings in the Feb. 23 issue of the science journal Physical Review Letters.

  The X particle was first observed in 2005 at the Fermi National Accelerator Laboratory during a failed search for dark matter. The unknown substance had puzzled physicists ever since because none of the prevailing theories could account for its characteristics.

  After making numerous calculations and comparisons, the trio asserted that the particle fit all the constraints of a Higgs bosons under the "next-to-minimal super-symmetric standard model."

  The "standard model" of particle physics stipulated in 1974 that there should exist a series of "elementary particles" -- including the boson hypothesized by Peter Higgs in 1964. Although all the other particles have been found, the Higgs boson remained elusive.

  Later in the 1980s, a new theory -- the "next-to-minimal super-symmetric standard model" -- was introduced, with a new assumption that there should exist seven kinds of Higgs boson particles and that every elementary particle should have a unique counterpart -- a super-symmetric particle.

  Since then, neither the Higgs bosons nor the super-symmetric particles have been observed.

  He noted that even though they didn't find "the" standard model Higgs boson, they found "something of even greater significance," meaning that by confirming the existence of particle X as one of the seven Higgs bosons, they could not only assert the existence of other Higgs bosons, but also expand the theoretical foundations of particle physics from the standard model to the next-to-minimal super-symmetric standard model.

  He added that by supporting the next-to-minimal super-symmetric standard model with their findings, the research on dark matter would enter a new stage -- because the theory also assumes that dark matter should be made of super-symmetric particles.

  "If the Higgs bosons exist, the super-symmetric particles could also exist," he said.

  He said the physicists needed more physical evidence to sustain the theory and that the Large Hadron Collider (LHC) project, which will come online in November, as well as the International Linear Collider (ILC), which is still in the planning stage, could reveal further evidence of the existence of other unknown particles.
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