Study of 'strange quarks' reveals their importance

Jefferson Lab scientists study one flavor of subatomic particles that appear in a fraction of a second.

Scientists at Jefferson Lab in Newport News announced Friday that ghostly subatomic particles called "strange quarks" contribute to a proton's electric and magnetic fields.

Why should you care?

Electromagnetism is important because it holds together the newspaper or computer screen you're looking at right now. It's the "glue" of all matter.

The magnetic field around a proton is the force behind medical instruments like the MRI -or Magnetic Resonance Imager, which helps doctors find abnormalities in the body's internal tissues and organs without making a cut.

"The way an MRI works is to grab a hold of the magnetism of a proton and spin it around," said Doug Beck, spokesperson for the G-Zero collaboration, an international group of 108 physicists from 19 research institutions. "We in our everyday lives rely on this magnetic field of the proton, but we don't know very much about where it comes from and how it's made up."

You have to delve deep into an atom to find quarks. They are inside protons, which are inside the nucleus of an atom. Physicists have long known that protons are primarily built of quarks and that quarks come in six flavors - up, down, strange, charm, bottom and top.

Strange quarks are the third lightest of all the flavors.

While up and down quarks always reside in the proton, strange quarks appear and vanish in a fraction of a second. To study quarks, scientists need a powerful instrument like Jefferson Lab's Continuous Electron Beam Accelerator Facility, or CEBAF, which sends a beam of electrons along an underground racetrack.

G-Zero scientists added a 100,000-pound magnet from Illinois and a fragile detector from France to CEBAF before operating the electron beam from December 2003 until May 2004. They alternated the electron beam's polarization, or spin, and studied how protons scattered off a hydrogen target.

It took them about a year to analyze the data before concluding that strange quarks influenced the charge distribution and magnetization of the protons. The G-Zero group will conduct another run of the electron beam in December.

"We don't know where it will lead," said Beck, a physics professor at the University of Illinois at Urbana-Champaign. "But the idea is to build our knowledge base."