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University of Mississippi

Physicists Receive NSF Grant to Search for New Subatomic Particles

Two University of Mississippi physicists have been awarded a competitive grant to build equipment to be used in the ongoing search for new subatomic particles.

The National Science Foundation major research instrumentation award for $798,819 is for development of a superconducting magnet coil and radio frequency cavity, which researchers hope to use to accelerate tiny particles called muons until they collide head-on, creating new kinds of subatomic particles. Muons are similar to electrons, but 200 times more massive.

The project is part of a worldwide effort to study the mass of neutrinos, tiny particles with no electrical charge, and to detect the elusive Higgs boson, the particle thought to hold the key to the relative masses of all other subatomic particles.

Donald Summers and Lucien Cremaldi, UM professors of physics and astronomy, are co-principal investigators for the two-year project. Both are longtime members of the university’s High Energy Physics Group, which is involved in several international projects to understand the fundamental forces of nature.

“The university, along with the Lawrence Berkley National Laboratory in California and the Thomas Jefferson National Accelerator Facility in Virginia, is making these cavities, which resemble very large and powerful microwave ovens,” Summers said. The radio frequency, or RF, cavities, made of copper, are about 5 feet in diameter and look like giant pill boxes. But instead of pills, these devices store high-power radio waves.

Radio waves consist of oscillating electric and magnetic fields, and the team plans to use the electric fields to accelerate electrically charged particles, such as muons.

“The muons ride an electric wave just like a surfer rides an ocean wave,” Summers explained. “Similarly, low-power radio waves from cell phone towers accelerate electrons in cell phone antennas to transmit phone calls.”

The muons, which are unstable and decay into other particles in just a fraction of a second, are made by colliding a beam of protons with a metal target, he said.

“This produces muons with a high temperature 50 million degrees Fahrenheit. We plan to cool them to 5,000 degrees Fahrenheit.”

The relatively cool muons are easier to handle, Cremaldi said.

“As the muons are cooled, they form compact swarms such that their collisions should generate the new matter,” he said.

To focus the muons as they are accelerated, the team uses a superconducting magnet coil. Each RF cavity is surrounded by a 6-foot-diameter-by-1-foot long wire coil.

“Three million amps of electricity will run through each coil, creating a magnetic field 100,000 times stronger than the field of the Earth,” Cremaldi said.

Instead of copper, the wire coils are made of nobium and titanium metals and cooled to minus 452 degrees Fahrenheit. This reduces the electrical resistance of the coil to zero, making it a “superconductor,” Summers said.

“If we used a copper coil to generate the magnetic field rather than a superconducting coil, it would consume 26 megawatts,” he said. “The UM campus consumes 18 megawatts.”

The ultimate goal is to get the RF cavities to accelerate muons until they can collide, Summers said. “That’s going to take a little bit of practice,” he said.

The project promises to help physicists better understand the fundamental principles of physics that hold the universe together, Cremaldi said.

“If successful, this acceleration experiment could be the next step toward the discovery of dark matter, the subatomic particles some astronomers have said comprise 90 percent of the mass of our Milky Way galaxy,” he said. “Dark matter holds the Milky Way galaxy together, but so far only its gravitational influence has been observed.”

Along with its collaborators, the UM team is to operate the RF cavities at the Fermi National Accelerator Laboratory near Chicago. FermiLab has agreed to supply the radio frequency power to the cavities and to supply beams of subatomic particles for the RF cavities to accelerate, Summers said.

Besides Cremaldi and Summers, the team includes several UM undergraduate and graduate physics students who will help gather data.

The team’s application for the grant was peer-reviewed and was among only a few chosen for funding, Summers said. The results of this project are eagerly awaited by researchers worldwide.

“One of the most critical components of accelerator research today is to investigate the performance limitations of very high-gradient radio frequency cavities operating in the presence of strong magnetic fields,” said Harold Kirk of Brookhaven National Laboratory in New York. “Mississippi’s work will be of great benefit to us at Brookhaven, and we wish UM the best of success with this project.”

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