Research pushes physics forward


Top quark experiment ‘great rehearsal' for discovery of elusive Higgs boson

An international team of physicists including researchers from McGill University has uncovered a rare mechanism that produces a single top quark, the heaviest known particle in nature — a breakthrough that brings the international physics community a step closer to its Holy Grail.

The DZero collaboration, involving 600 scientists in more than 20 countries, used sophisticated analysis techniques to sift through a million billion proton-antiproton collisions to observe about 60 collisions containing a single top quark. The experiment was conducted at the U.S. Department of Energy's Fermi National Accelerator Laboratory (Fermilab) near Chicago using the Tevatron, the world's most powerful particle collider.

"There are two reasons everyone in the physics world is excited about this: it's a new, direct test of the Standard Model of particle physics, and it was an extremely challenging experiment involving huge amounts of sifting that amounted to searching for a needle in a very large haystack," said Brigitte Vachon, a Canada Research Chair in Particle Physics and team leader of the McGill members of DZero. "This is exactly the kind of challenge we face while looking for the Higgs boson. This is proof that we can get to it. It's a great rehearsal."

The elusive Higgs boson — considered the Holy Grail of particle physics — is a force field that scientists believe could explain the origins of mass. Dr Peter Higgs of the University of Edinburgh proposed its existence in 1964; however, the Higgs boson has never been observed in the laboratory and currently exists only in the form of a theoretical mathematical equation.

"It's something in the universe that provides drag, like walking through a pool of water, and results in the mass of a particle," explained Vachon. "Finding the Higgs boson and studying its properties would be a collective success for scientists around the world because it would help us better understand our universe."

The quest is continuing in earnest, Vachon said, with the so-called "next generation" of particle physics experiments at laboratories such as CERN in Geneva expected to begin later this year.

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