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LHC Gaining In The Hunt For Elusive Particle

July 25, 2010

The Large Hadron Collider (LHC) is giving physicists hopeful candidates in the hunt for the heaviest elementary particle known to science.

According to BBC News, so far their observations have been leading them in that direction.

If the observations can be confirmed, it would be a first for Europe as the top quark particle has only been generated in one lab in the US.

Dr Arnaud Lucotte, from the French National Centre of Scientific Research (CNRS), said the discovery could help physicists in the hunt for the elusive Higgs boson — the God particle.

The details of the top quark candidates were presented at The International Conference on High Energy Physics (ICHEP), which runs from July 22 to 28 in Paris.

The LHC is operated by the European Organization for Nuclear Research (CERN), based in Geneva, near the French-Swiss border.

Several possible detections of top quarks have been recently made by the LHC’s Atlas and Compact Muon Solenoid (CMS) experiments.

Atlas has detected nine collision events compatible with the top quark; CMS has made 3 to 4 observations of possible candidates. Physicists stressed, however, that more data was needed in order to support the conclusive observation of top quark production.

A detection of top quarks would represent a small milestone for CERN, which is making steady progress after the accident which forced it to shut down for 14 months shortly after it was turned on in 2008.

The top quark was discovered in 1995 by the Tevatron accelerator, operated by Fermilab in Illinois. Since then, the US accelerator has produced them in abundance. But they have never been produced outside Fermilab.

Tim Christiansen said, in a presentation at ICHEP, that events observed by the CMS experiment included one “striking” top quark candidate.

Dr Lucotte told BBC News that the top quark was “well coupled” to the Higgs boson. In other words, there is thought to be a special interaction between these two particles.

Despite trying to produce the Higgs for decades, particle physicists have so far failed in that attempt. The Higgs boson is crucial to the current theory which has been conceived to explain the interactions of sub-atomic particles, known as the Standard Model.

Rival physicists working at the Tevatron accelerator in the US, however, now believe the Higgs is within reach. They hope to detect the elusive particle themselves, especially if the Tevatron’s lifetime can be extended to 2014, which is currently under discussion.

If the Higgs boson exists in a form known as the charged Higgs, Dr Lucotte explained, the top quark could be crucial to detecting it.

Elementary particles generated at colliders “decay”, or transform, into other sub-atomic particles, which may or may not be stable. The close coupling of the charged Higgs to the top quark means that, if the Higgs boson is heavier than the top quark, it might reveal itself by decaying into a top quark and another particle known as a b-quark. If the Higgs is lighter, then the top quark might decay into a Higgs and a b-quark.

Other physicists foresee a different type of Higgs, one which fits the restrictions of the Standard Model. The top quark might also act as the originator for so-called “super-symmetric” particles. These would represent an entirely new class of particles, predicted to exist by theorists, but which have yet to be observed at particle accelerators.

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