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U.S. lab outwits Europe's supercollider in particle testing

Posted: 15 Sep 2008 ?? ?Print Version ?Bookmark and Share

Keywords:supercollider? accelerator? particle?

A U.S. laboratory claims to beat out Europe's new supercollider for the world's first observation of a new subatomic particle.

The Fermi National Accelerator Laboratory one-upped the European Council for Nuclear Research's CERN's Large Hadron Collider by announcing the observation of the Omega b baryon, related to the proton. By colliding protons with antiprotons, Fermilab became the first to observe the particle. But its discovery may yet be confirmed by CERN next spring when CERN ramps up its larger particle accelerator.

"Omega b bayon is a distant relative of the proton and neutron from which the universe is made along with electrons," said Jianming Qian, professor of the University of Michigan, which helped conduct the experiment to observe the Omega b bayon. "Protons and neutrons are the lightest elements in the baryon family, but Omega b is six times heavier than a proton," he added.

Qian discovered the Omega b baryon as a member of the DZero project at Fermilab. In all, 600 physicists from 90 institutions are analyzing data from the DZero project. They must sift through data from over 100 trillion particle collisions to find the 18 events with the distinctive decay profile confirming the observation of the Omega b baryon, which travelled only 1mm before decaying.

Group members
Baryons are composed of quarks from three families: up/down, charm/strange and top/bottom. Protons and neutrons are made from up and down quarks, the first family. The Omega b baryon, meanwhile, was found at Fermilab consisting of quarks from the other two families such as two strange quarks and one bottom quark.

The Omega b baryon and other exotic particles, which last for only about 10s to 12s before decaying, are almost nonexistent, but were abundant just after the Big Bang. Almost all subatomic particles, except protons and electrons, are unstable and quickly decay. Even neutrons, composed of one "up" and two "down" quarks, are unstable by themselves and decay into a proton, an electron and an antineutrino.

Flexible utility
Particle accelerators are not designed specifically to observe particles like the Omega b bayon. Rather, both Fermilab and CERN are searching for the Higgs bosons, sometimes called the "God particle," which is a member of a more fundamental class of particles that are postulated as responsible for gravity a measurement of mass.

There is no confirmed explanation for why subatomic particles have any mass at all, which leaves the force of gravity in a theoretical state of limbo, with many competing theories attempting to explain it. Only by observing the decay of a Higgs boson, according to Qian, will theorists be able to resolve their differences.

"If we can observe Higgs boson decay, then we may be able to confirm what is called the Standard Model. Through this, we may discover that there are extra dimensions in space where only gravity can propagate. Our observations may lead to something entirely new," said Qian.

Both Fermi and CERN are looking for the Higgs boson using similar methods of accelerating particle beams to near the speed of light, then colliding them with a force almost as powerful as the Big Bang. Whereas CERN will use high-intensity proton beams, Fermilab's DZero project is using one beam of protons and one beam of antiprotons.

Since antiprotons must be painstakingly manufactured at a temperature of 17 trillion F, CERN researchers will not be able to create enough of them for its high-intensity beam. Fermilabs, however, uses a beam of lower intensity for which it can manufacture sufficient antiproton matter. The approach has paid off since proton/antiproton collisions create much more energy by virtue of mutual annihilation, resulting in the recent observation of the Omega b baryon.

The DZero project is funded by the U.S. Energy Department and the National Science Foundation.

- R. Colin Johnson
EE Times

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