It’s a material world

For several decades now, some of the world’s brightest physicists have been trying to figure out how rocks, and water, and air, and all the other stuff in the universe came to be.

The reason this question is so interesting is because in theory, there shouldn’t be any stuff in the universe at all.

“If you go into a lab and convert energy into matter, you produce matter and antimatter,” said Nigel Lockyer, professor of physics. For instance, a collision of two photons (energy) produces an electron (matter) and an anti-electron (antimatter).

“If matter and antimatter were equal,” he said, “you’d have a universe of only photons.”

But instead, we have a universe of planets and stars. Clearly, then, the scale must have been tipped ever so slightly in favor of matter.

Physics Professor Nigel Lockyer and University of Illinois researcher Kevin Pitts work on a portion of the new CDF detector array. The chips in the array that process the signals are being manufactured at Penn.

Fermilab photo

Lockyer is part of a team working on a device known as CDF — the Collider Detector at Fermilab, the U.S. Department of Energy’s particle-physics laboratory in Batavia, Ill. The CDF project, which involves more than 600 physicists from around the world, seeks to build on a 35-year-old discovery that offered the first clues as to why our universe is mostly matter.

That discovery, which was made when a team of physicists observing the decay of the strange quark noted that the particles and anti-particles decayed at different rates — the first observed instance of “charge-parity symmetry (CP) violation.”

Two members of that team, Val Fitch of Princeton and Jim Cronin of the University of Chicago, shared a Nobel Prize for this discovery. But neither they nor anyone else has been able to build upon it until recently. And this is where Lockyer and his colleagues come in.

Lockyer, senior research associate Joel Heinrich and Kevin Pitts of the University of Illinois earlier this year reported evidence of CP asymmetry in a second experiment, conducted at CDF, using the heavier bottom quark. Although expected in the Standard Model of particle physics, no previous experiment has ever succeeded in demonstrating CP asymmetry in the bottom quark.

The experiment could ultimately lead to an explanation of why we exist. “It is generally accepted that the amount of CP violation in the Standard Model is not enough to explain the expansion of the universe,” Lockyer said. “We expect something to show itself.”

And physicists everywhere are now rushing to find that something. New facilities dedicated to producing B mesons are being built at Fermilab, at Stanford University and in Germany and Japan. Penn’s physics department is involved in building a key piece of the Fermilab device — the microchips that will process the signals picked up by the detectors in the collider.

While Lockyer and his colleagues stressed the tentativeness of their initial findings, Lockyer is hardly reticent about their potential. “Within five to 10 years, we should know everything there is to know about CP violation in the B system,” he said.

Front page for this issue | Pennsylvania Current home page

Originally published on September 16, 1999