Researchers Help Find New Sub-atomic Particle

The discovery was made by physicists of the DZero experiment at the U.S. Department of Energy's Fermi National Accelerator Laboratory in Batavia, Ill.

Discovery and measurement of the particle's mass will provide new understanding about the basic building blocks of matter.

Local participants in the experiment were physics faculty members Z.D. Greenwood, Lee Sawyer and Markus Wobisch; former post-doctoral researcher Julie Kalk; and current post-doctoral scientists Mike Arov and Joe Steele.

"We've never seen anything like this before," said Sawyer, who is academic director of Tech's physics and chemistry programs. "What is really neat about this is that we have models that predict these things' existence. Discovery is verification of the Standard Model of particle physics".

The Tech team built electronics for part of the DZero detector, which records the path, energy and charge of the particles released during the sub-atomic collisions that are necessary for the project.

"That was a big job," said Greenwood, an associate professor of physics. "It was designed and put together right here at Tech".

In describing Tech's contribution to this frontier of physics, Greenwood said, "Because we are dealing with fundamental particles and trying to understand and contribute to material that describes how the whole universe works, we're necessarily operating at the cutting edge".

In addition to helping build the detector, which is about the size of a three-story house, Tech plays a significant role in processing the data gathered from the detector.

Details of the discovery will be presented at a special Fermilab seminar at 1 p.m. Friday, June 15. The DZero experiment reported the discovery of the particle in a paper submitted June 12 to Physical Review Letters, the Journal of the American Physical Society.

A news release from Fermilab provided the following information:

• The newly discovered heavy particle is a baryon known as the "cascade b."
• A baryon is a particle of matter made of three fundamental building blocks called quarks. The most familiar baryons are the proton and neutron of the atomic nucleus. Baryons composed of heavier quarks, including the cascade b, were abundant soon after the Big Bang at the beginning of the universe."
• The discovery and measurement of cascade b's mass provide new insight into how the strong nuclear force acts upon those basic building blocks of matter.
• Cascade b is the first observed baryon formed of quarks from all three families of matter.
• Previous to this discovery, only indirect evidence for cascade b had been reported by experiments at the Large Electron-Positron collider at the CERN Laboratory near Geneva, Switzerland.
• Cascade b is produced in high-energy proton-antiproton collisions at Fermilab's Tevatron device.

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Physicist Robin Staffin, associate director for high-energy physics for the Department of Energy's Office of Science, said, "Knowing the mass of the cascade b baryon gives researchers information they need in order to develop accurate models of how individual quarks are bound together into larger particles such as protons and neutrons".

DZero is an international experiment of about 610 physicists from 88 institutions in 19 countries. It is supported by the Department of Energy, the National Science Foundation and many international funding agencies. Fermilab is a national laboratory funded by DOE's Office of Science, operated under contract by Fermi Research Alliance.

More information about the discovery can be found at this Fermilab Web site.

Tech scientists are also working on a related project that will continue after the DZero experiment ends. In Sweden, on a next generation experiment called ATLAS, they will attempt to discover the Higgs Particle, which determines why everything in the universe has mass.

The search for the Higgs, also a goal of DZero, has thus far not been realized. Chances for a discovery of the elusive Higgs particle will be enhanced by the larger, more powerful ATLAS experiment, Greenwood said.


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